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Author SHA1 Message Date
Lorenzo Stoakes
8b2914162a mm/mseal: small cleanups 
Drop the wholly unnecessary set_vma_sealed() helper(), which is used only
once, and place VMA_ITERATOR() declarations in the correct place.

Retain vma_is_sealed(), and use it instead of the confusingly named
can_modify_vma(), so it's abundantly clear what's being tested, rather
then a nebulous sense of 'can the VMA be modified'.

No functional change intended.

Link: https://lkml.kernel.org/r/98cf28d04583d632a6eb698e9ad23733bb6af26b.1753431105.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Jeff Xu <jeffxu@chromium.org>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-08-02 12:06:09 -07:00
Dev Jain
cac1db8c3a mm: optimize mprotect() by PTE batching 
Use folio_pte_batch to batch process a large folio.  Note that, PTE
batching here will save a few function calls, and this strategy in certain
cases (not this one) batches atomic operations in general, so we have a
performance win for all arches.  This patch paves the way for patch 7
which will help us elide the TLBI per contig block on arm64.

The correctness of this patch lies on the correctness of setting the new
ptes based upon information only from the first pte of the batch (which
may also have accumulated a/d bits via modify_prot_start_ptes()).

Observe that the flag combination we pass to mprotect_folio_pte_batch()
guarantees that the batch is uniform w.r.t the soft-dirty bit and the
writable bit.  Therefore, the only bits which may differ are the a/d bits.
So we only need to worry about code which is concerned about the a/d bits
of the PTEs.

Setting extra a/d bits on the new ptes where previously they were not set,
is fine - setting access bit when it was not set is not an incorrectness
problem but will only possibly delay the reclaim of the page mapped by the
pte (which is in fact intended because the kernel just operated on this
region via mprotect()!).  Setting dirty bit when it was not set is again
not an incorrectness problem but will only possibly force an unnecessary
writeback.

So now we need to reason whether something can go wrong via
can_change_pte_writable().  The pte_protnone, pte_needs_soft_dirty_wp, and
userfaultfd_pte_wp cases are solved due to uniformity in the corresponding
bits guaranteed by the flag combination.  The ptes all belong to the same
VMA (since callers guarantee that [start, end) will lie within the VMA)
therefore the conditional based on the VMA is also safe to batch around.

Since the dirty bit on the PTE really is just an indication that the folio
got written to - even if the PTE is not actually dirty but one of the PTEs
in the batch is, the wp-fault optimization can be made.  Therefore, it is
safe to batch around pte_dirty() in can_change_shared_pte_writable() (in
fact this is better since without batching, it may happen that some ptes
aren't changed to writable just because they are not dirty, even though
the other ptes mapping the same large folio are dirty).

To batch around the PageAnonExclusive case, we must check the
corresponding condition for every single page.  Therefore, from the large
folio batch, we process sub batches of ptes mapping pages with the same
PageAnonExclusive condition, and process that sub batch, then determine
and process the next sub batch, and so on.  Note that this does not cause
any extra overhead; if suppose the size of the folio batch is 512, then
the sub batch processing in total will take 512 iterations, which is the
same as what we would have done before.

For pte_needs_flush():

ppc does not care about the a/d bits.

For x86, PAGE_SAVED_DIRTY is ignored.  We will flush only when a/d bits
get cleared; since we can only have extra a/d bits due to batching, we
will only have an extra flush, not a case where we elide a flush due to
batching when we shouldn't have.

Link: https://lkml.kernel.org/r/20250718090244.21092-7-dev.jain@arm.com
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Cc: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-07-24 19:12:41 -07:00
Dev Jain
45199f715b mm: split can_change_pte_writable() into private and shared parts 
In preparation for patch 6 and modularizing the code in general, split
can_change_pte_writable() into private and shared VMA parts.  No
functional change intended.

Link: https://lkml.kernel.org/r/20250718090244.21092-6-dev.jain@arm.com
Signed-off-by: Dev Jain <dev.jain@arm.com>
Suggested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Cc: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-07-24 19:12:41 -07:00
Dev Jain
0aa3657df3 mm: add batched versions of ptep_modify_prot_start/commit 
Batch ptep_modify_prot_start/commit in preparation for optimizing
mprotect, implementing them as a simple loop over the corresponding single
pte helpers.  Architecture may override these helpers.

Link: https://lkml.kernel.org/r/20250718090244.21092-4-dev.jain@arm.com
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Cc: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-07-24 19:12:40 -07:00
Dev Jain
1d40f4e3d9 mm: optimize mprotect() for MM_CP_PROT_NUMA by batch-skipping PTEs 
For the MM_CP_PROT_NUMA skipping case, observe that, if we skip an
iteration due to the underlying folio satisfying any of the skip
conditions, then for all subsequent ptes which map the same folio, the
iteration will be skipped for them too.  Therefore, we can optimize by
using folio_pte_batch() to batch skip the iterations.

Use prot_numa_skip() introduced in the previous patch to determine whether
we need to skip the iteration.  Change its signature to have a double
pointer to a folio, which will be used by mprotect_folio_pte_batch() to
determine the number of iterations we can safely skip.

Link: https://lkml.kernel.org/r/20250718090244.21092-3-dev.jain@arm.com
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Cc: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-07-24 19:12:40 -07:00
Dev Jain
b9bf6c2872 mm: refactor MM_CP_PROT_NUMA skipping case into new function 
Patch series "Optimize mprotect() for large folios", v5.

Use folio_pte_batch() to optimize change_pte_range().  On arm64, if the
ptes are painted with the contig bit, then ptep_get() will iterate through
all 16 entries to collect a/d bits.  Hence this optimization will result
in a 16x reduction in the number of ptep_get() calls.  Next,
ptep_modify_prot_start() will eventually call contpte_try_unfold() on
every contig block, thus flushing the TLB for the complete large folio
range.  Instead, use get_and_clear_full_ptes() so as to elide TLBIs on
each contig block, and only do them on the starting and ending contig
block.

For split folios, there will be no pte batching; the batch size returned
by folio_pte_batch() will be 1.  For pagetable split folios, the ptes will
still point to the same large folio; for arm64, this results in the
optimization described above, and for other arches, a minor improvement is
expected due to a reduction in the number of function calls.

mm-selftests pass on arm64.  I have some failing tests on my x86 VM
already; no new tests fail as a result of this patchset.

We use the following test cases to measure performance, mprotect()'ing the
mapped memory to read-only then read-write 40 times:

Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then
pte-mapping those THPs
Test case 2: Mapping 1G of memory with 64K mTHPs
Test case 3: Mapping 1G of memory with 4K pages

Average execution time on arm64, Apple M3:
Before the patchset:
T1: 2.1 seconds   T2: 2 seconds   T3: 1 second

After the patchset:
T1: 0.65 seconds   T2: 0.7 seconds   T3: 1.1 seconds

Observing T1/T2 and T3 before the patchset, we also remove the regression
introduced by ptep_get() on a contpte block.  And, for large folios we get
an almost 74% performance improvement, albeit the trade-off being a slight
degradation in the small folio case.

For x86:
Before the patchset:
T1: 3.75 seconds  T2: 3.7 seconds  T3: 3.85 seconds

After the patchset:
T1: 3.7 seconds  T2: 3.7 seconds  T3: 3.9 seconds

So there is a minor improvement due to reduction in number of function
calls, and a slight degradation in the small folio case due to the
overhead of vm_normal_folio() + folio_test_large().

Here is the test program:

 #define _GNU_SOURCE
 #include <sys/mman.h>
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 #include <unistd.h>

 #define SIZE (1024*1024*1024)

unsigned long pmdsize = (1UL << 21);
unsigned long pagesize = (1UL << 12);

static void pte_map_thps(char *mem, size_t size)
{
	size_t offs;
	int ret = 0;


	/* PTE-map each THP by temporarily splitting the VMAs. */
	for (offs = 0; offs < size; offs += pmdsize) {
		ret |= madvise(mem + offs, pagesize, MADV_DONTFORK);
		ret |= madvise(mem + offs, pagesize, MADV_DOFORK);
	}

	if (ret) {
		fprintf(stderr, "ERROR: mprotect() failed\n");
		exit(1);
	}
}

int main(int argc, char *argv[])
{
	char *p;
        int ret = 0;
	p = mmap((1UL << 30), SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	if (p != (1UL << 30)) {
		perror("mmap");
		return 1;
	}



	memset(p, 0, SIZE);
	if (madvise(p, SIZE, MADV_NOHUGEPAGE))
		perror("madvise");
	explicit_bzero(p, SIZE);
	pte_map_thps(p, SIZE);

	for (int loops = 0; loops < 40; loops++) {
		if (mprotect(p, SIZE, PROT_READ))
			perror("mprotect"), exit(1);
		if (mprotect(p, SIZE, PROT_READ|PROT_WRITE))
			perror("mprotect"), exit(1);
		explicit_bzero(p, SIZE);
	}
}


This patch (of 7):

Reduce indentation by refactoring the prot_numa case into a new function. 
No functional change intended.

Link: https://lkml.kernel.org/r/20250718090244.21092-1-dev.jain@arm.com
Link: https://lkml.kernel.org/r/20250718090244.21092-2-dev.jain@arm.com
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Cc: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-07-24 19:12:40 -07:00
Alistair Popple
8a6a984c2e mm: remove redundant pXd_devmap calls 
DAX was the only thing that created pmd_devmap and pud_devmap entries
however it no longer does as DAX pages are now refcounted normally and
pXd_trans_huge() returns true for those.  Therefore checking both
pXd_devmap and pXd_trans_huge() is redundant and the former can be removed
without changing behaviour as it will always be false.

Link: https://lkml.kernel.org/r/d58f089dc16b7feb7c6728164f37dea65d64a0d3.1750323463.git-series.apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: Björn Töpel <bjorn@kernel.org>
Cc: Björn Töpel <bjorn@rivosinc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Deepak Gupta <debug@rivosinc.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Inki Dae <m.szyprowski@samsung.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Groves <john@groves.net>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-07-09 22:42:17 -07:00
Lorenzo Stoakes
bfbe71109f mm: update core kernel code to use vm_flags_t consistently 
The core kernel code is currently very inconsistent in its use of
vm_flags_t vs.  unsigned long.  This prevents us from changing the type of
vm_flags_t in the future and is simply not correct, so correct this.

While this results in rather a lot of churn, it is a critical
pre-requisite for a future planned change to VMA flag type.

Additionally, update VMA userland tests to account for the changes.

To make review easier and to break things into smaller parts, driver and
architecture-specific changes is left for a subsequent commit.

The code has been adjusted to cascade the changes across all calling code
as far as is needed.

We will adjust architecture-specific and driver code in a subsequent patch.

Overall, this patch does not introduce any functional change.

Link: https://lkml.kernel.org/r/d1588e7bb96d1ea3fe7b9df2c699d5b4592d901d.1750274467.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Kees Cook <kees@kernel.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-07-09 22:42:13 -07:00
Gavin Guo
b960818d51 mm/huge_memory: remove useless folio pointers passing 
Since the previous commit "mm/huge_memory: Adjust try_to_migrate_one() and
split_huge_pmd_locked()" has simplified the logic by leveraging the folio
verification in page_vma_mapped_walk(), this patch removes the unnecessary
folio pointers passing.

Link: https://lkml.kernel.org/r/20250425103859.825879-3-gavinguo@igalia.com
Link: https://lore.kernel.org/all/98d1d195-7821-4627-b518-83103ade56c0@redhat.com/
Link: https://lore.kernel.org/all/91599a3c-e69e-4d79-bac5-5013c96203d7@redhat.com/
Signed-off-by: Gavin Guo <gavinguo@igalia.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Florent Revest <revest@google.com>
Cc: Gavin Shan <gshan@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-05-12 23:50:34 -07:00
David Hildenbrand
003fde4492 mm: convert folio_likely_mapped_shared() to folio_maybe_mapped_shared() 
Let's reuse our new MM ownership tracking infrastructure for large folios
to make folio_likely_mapped_shared() never return false negatives -- never
indicating "not mapped shared" although the folio *is* mapped shared. 
With that, we can rename it to folio_maybe_mapped_shared() and get rid of
the dependency on the mapcount of the first folio page.

The semantics are now arguably clearer: no mixture of "false negatives"
and "false positives", only the remaining possibility for "false
positives".

Thoroughly document the new semantics.  We might now detect that a large
folio is "maybe mapped shared" although it *no longer* is -- but once was.
Now, if more than two MMs mapped a folio at the same time, and the MM
mapping the folio exclusively at the end is not one tracked in the two
folio MM slots, we will detect the folio as "maybe mapped shared".

For anonymous folios, usually (except weird corner cases) all PTEs that
target a "maybe mapped shared" folio are R/O.  As soon as a child process
would write to them (iow, actively use them), we would CoW and effectively
replace these PTEs.  Most cases (below) are not expected to really matter
with large anonymous folios for this reason.

Most importantly, there will be no change at all for:
* small folios
* hugetlb folios
* PMD-mapped PMD-sized THPs (single mapping)

This change has the potential to affect existing callers of
folio_likely_mapped_shared() -> folio_maybe_mapped_shared():

(1) fs/proc/task_mmu.c: no change (hugetlb)

(2) khugepaged counts PTEs that target shared folios towards
    max_ptes_shared (default: HPAGE_PMD_NR / 2), meaning we could skip a
    collapse where we would have previously collapsed.  This only applies
    to anonymous folios and is not expected to matter in practice.

    Worth noting that this change sorts out case (A) documented in
    commit 1bafe96e89 ("mm/khugepaged: replace page_mapcount() check by
    folio_likely_mapped_shared()") by removing the possibility for "false
    negatives".

(3) MADV_COLD / MADV_PAGEOUT / MADV_FREE will not try splitting
    PTE-mapped THPs that are considered shared but not fully covered by
    the requested range, consequently not processing them.

    PMD-mapped PMD-sized THP are not affected, or when all PTEs are
    covered.  These functions are usually only called on anon/file folios
    that are exclusively mapped most of the time (no other file mappings
    or no fork()), so the "false negatives" are not expected to matter in
    practice.

(4) mbind() / migrate_pages() / move_pages() will refuse to migrate
    shared folios unless MPOL_MF_MOVE_ALL is effective (requires
    CAP_SYS_NICE).  We will now reject some folios that could be migrated.

    Similar to (3), especially with MPOL_MF_MOVE_ALL, so this is not
    expected to matter in practice.

    Note that cpuset_migrate_mm_workfn() calls do_migrate_pages() with
    MPOL_MF_MOVE_ALL.

(5) NUMA hinting

    mm/migrate.c:migrate_misplaced_folio_prepare() will skip file
    folios that are probably shared libraries (-> "mapped shared" and
    executable).  This check would have detected it as a shared library at
    some point (at least 3 MMs mapping it), so detecting it afterwards
    does not sound wrong (still a shared library).  Not expected to
    matter.

    mm/memory.c:numa_migrate_check() will indicate TNF_SHARED in
    MAP_SHARED file mappings when encountering a shared folio.  Similar
    reasoning, not expected to matter.

    mm/mprotect.c:change_pte_range() will skip folios detected as
    shared in CoW mappings.  Similarly, this is not expected to matter in
    practice, but if it would ever be a problem we could relax that check
    a bit (e.g., basing it on the average page-mapcount in a folio),
    because it was only an optimization when many (e.g., 288) processes
    were mapping the same folios -- see commit 859d4adc34 ("mm: numa: do
    not trap faults on shared data section pages.")

(6) mm/rmap.c:folio_referenced_one() will skip exclusive swapbacked
    folios in dying processes.  Applies to anonymous folios only.  Without
    "false negatives", we'll now skip all actually shared ones.  Skipping
    ones that are actually exclusive won't really matter, it's a pure
    optimization, and is not expected to matter in practice.

In theory, one can detect the problematic scenario: folio_mapcount() > 0
and no folio MM slot is occupied ("state unknown").  One could reset the
MM slots while doing an rmap walk, which migration / folio split already
do when setting everything up.  Further, when batching PTEs we might
naturally learn about a owner (e.g., folio_mapcount() == nr_ptes) and
could update the owner.  However, we'll defer that until the scenarios
where it would really matter are clear.

Link: https://lkml.kernel.org/r/20250303163014.1128035-15-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andy Lutomirks^H^Hski <luto@kernel.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Michal Koutn <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: tejun heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-03-17 22:06:46 -07:00
Lorenzo Stoakes
e92b6e7bb6 mm: use READ/WRITE_ONCE() for vma->vm_flags on migrate, mprotect 
According to the syzbot report referenced here, it is possible to
encounter a race between mprotect() writing to the vma->vm_flags field and
migration checking whether the VMA is locked.

There is no real problem with timing here per se, only that torn
reads/writes may occur.  Therefore, as a proximate fix, ensure both
operations READ_ONCE() and WRITE_ONCE() to avoid this.

This race is possible due to the ability to look up VMAs via the rmap,
which migration does in this case, which takes no mmap or VMA lock and
therefore does not preclude an operation to modify a VMA.

When the final update of VMA flags is performed by mprotect, this will
cause the rmap lock to be taken while the VMA is inserted on split/merge.

However the means by which we perform splits/merges in the kernel is that
we perform the split/merge operation on the VMA, acquiring/releasing locks
as needed, and only then, after having done so, modifying fields.

We should carefully examine and determine whether we can combine the two
operations so as to avoid such races, and whether it might be possible to
otherwise annotate these rmap field accesses.

Link: https://lkml.kernel.org/r/20250207172442.78836-1-lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reported-by: syzbot+c2e5712cbb14c95d4847@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/67a34e60.050a0220.50516.0040.GAE@google.com/
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-03-16 22:06:09 -07:00
David Hildenbrand
c25465eb76 mm: use single SWP_DEVICE_EXCLUSIVE entry type 
There is no need for the distinction anymore; let's merge the readable and
writable device-exclusive entries into a single device-exclusive entry
type.

Link: https://lkml.kernel.org/r/20250210193801.781278-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Simona Vetter <simona.vetter@ffwll.ch>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Tested-by: Alistair Popple <apopple@nvidia.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Karol Herbst <kherbst@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Lyude <lyude@redhat.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yanteng Si <si.yanteng@linux.dev>
Cc: Barry Song <v-songbaohua@oppo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-03-16 22:05:58 -07:00
Lorenzo Stoakes
7c53dfbdb0 mm: add PTE_MARKER_GUARD PTE marker 
Add a new PTE marker that results in any access causing the accessing
process to segfault.

This is preferable to PTE_MARKER_POISONED, which results in the same
handling as hardware poisoned memory, and is thus undesirable for cases
where we simply wish to 'soft' poison a range.

This is in preparation for implementing the ability to specify guard pages
at the page table level, i.e.  ranges that, when accessed, should cause
process termination.

Additionally, rename zap_drop_file_uffd_wp() to zap_drop_markers() - the
function checks the ZAP_FLAG_DROP_MARKER flag so naming it for this single
purpose was simply incorrect.

We then reuse the same logic to determine whether a zap should clear a
guard entry - this should only be performed on teardown and never on
MADV_DONTNEED or MADV_FREE.

We additionally add a WARN_ON_ONCE() in hugetlb logic should a guard
marker be encountered there, as we explicitly do not support this
operation and this should not occur.

Link: https://lkml.kernel.org/r/f47f3d5acca2dcf9bbf655b6d33f3dc713e4a4a0.1730123433.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Vlastimil Babka <vbabkba@suse.cz>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Suggested-by: Jann Horn <jannh@google.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Helge Deller <deller@gmx.de>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-11-11 00:26:44 -08:00
Lorenzo Stoakes
0fb4a7ad27 mm: refactor map_deny_write_exec() 
Refactor the map_deny_write_exec() to not unnecessarily require a VMA
parameter but rather to accept VMA flags parameters, which allows us to
use this function early in mmap_region() in a subsequent commit.

While we're here, we refactor the function to be more readable and add
some additional documentation.

Link: https://lkml.kernel.org/r/6be8bb59cd7c68006ebb006eb9d8dc27104b1f70.1730224667.git.lorenzo.stoakes@oracle.com
Fixes: deb0f65628 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reported-by: Jann Horn <jannh@google.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Jann Horn <jannh@google.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Helge Deller <deller@gmx.de>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-11-05 16:49:55 -08:00
Pedro Falcato
4a2dd02b09 mm/mprotect: replace can_modify_mm with can_modify_vma 
Avoid taking an extra trip down the mmap tree by checking the vmas
directly.  mprotect (per POSIX) tolerates partial failure.

Link: https://lkml.kernel.org/r/20240817-mseal-depessimize-v3-3-d8d2e037df30@gmail.com
Signed-off-by: Pedro Falcato <pedro.falcato@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-09-03 21:15:41 -07:00
Peter Xu
cb0f01beb1 mm/mprotect: fix dax pud handlings 
This is only relevant to the two archs that support PUD dax, aka, x86_64
and ppc64.  PUD THPs do not yet exist elsewhere, and hugetlb PUDs do not
count in this case.

DAX have had PUD mappings for years, but change protection path never
worked.  When the path is triggered in any form (a simple test program
would be: call mprotect() on a 1G dev_dax mapping), the kernel will report
"bad pud".  This patch should fix that.

The new change_huge_pud() tries to keep everything simple.  For example,
it doesn't optimize write bit as that will need even more PUD helpers. 
It's not too bad anyway to have one more write fault in the worst case
once for 1G range; may be a bigger thing for each PAGE_SIZE, though. 
Neither does it support userfault-wp bits, as there isn't such PUD
mappings that is supported; file mappings always need a split there.

The same to TLB shootdown: the pmd path (which was for x86 only) has the
trick of using _ad() version of pmdp_invalidate*() which can avoid one
redundant TLB, but let's also leave that for later.  Again, the larger the
mapping, the smaller of such effect.

There's some difference on handling "retry" for change_huge_pud() (where
it can return 0): it isn't like change_huge_pmd(), as the pmd version is
safe with all conditions handled in change_pte_range() later, thanks to
Hugh's new pte_offset_map_lock().  In short, change_pte_range() is simply
smarter.  For that, change_pud_range() will need proper retry if it races
with something else when a huge PUD changed from under us.

The last thing to mention is currently the PUD path ignores the huge pte
numa counter (NUMA_HUGE_PTE_UPDATES), not only because DAX is not
applicable to NUMA, but also that it's ambiguous on its own to decide how
to account pud in this case.  In one earlier version of this patchset I
proposed to remove the counter as it doesn't even look right to do the
accounting as of now [1], but then a further discussion suggests we can
leave that for later, as that doesn't block this series if we choose to
ignore that counter.  That's what this patch does, by ignoring it.

When at it, touch up the comment in pgtable_split_needed() to make it
generic to either pmd or pud file THPs.

[1] https://lore.kernel.org/all/20240715192142.3241557-3-peterx@redhat.com/
[2] https://lore.kernel.org/r/added2d0-b8be-4108-82ca-1367a388d0b1@redhat.com

Link: https://lkml.kernel.org/r/20240812181225.1360970-8-peterx@redhat.com
Fixes: a00cc7d9dd ("mm, x86: add support for PUD-sized transparent hugepages")
Fixes: 27af67f356 ("powerpc/book3s64/mm: enable transparent pud hugepage")
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-09-01 20:26:10 -07:00
Peter Xu
7f06e3aa2e mm/mprotect: push mmu notifier to PUDs 
mprotect() does mmu notifiers in PMD levels.  It's there since 2014 of
commit a5338093bf ("mm: move mmu notifier call from change_protection to
change_pmd_range").

At that time, the issue was that NUMA balancing can be applied on a huge
range of VM memory, even if nothing was populated.  The notification can
be avoided in this case if no valid pmd detected, which includes either
THP or a PTE pgtable page.

Now to pave way for PUD handling, this isn't enough.  We need to generate
mmu notifications even on PUD entries properly.  mprotect() is currently
broken on PUD (e.g., one can easily trigger kernel error with dax 1G
mappings already), this is the start to fix it.

To fix that, this patch proposes to push such notifications to the PUD
layers.

There is risk on regressing the problem Rik wanted to resolve before, but I
think it shouldn't really happen, and I still chose this solution because
of a few reasons:

  1) Consider a large VM that should definitely contain more than GBs of
  memory, it's highly likely that PUDs are also none.  In this case there
  will have no regression.

  2) KVM has evolved a lot over the years to get rid of rmap walks, which
  might be the major cause of the previous soft-lockup.  At least TDP MMU
  already got rid of rmap as long as not nested (which should be the major
  use case, IIUC), then the TDP MMU pgtable walker will simply see empty VM
  pgtable (e.g. EPT on x86), the invalidation of a full empty region in
  most cases could be pretty fast now, comparing to 2014.

  3) KVM has explicit code paths now to even give way for mmu notifiers
  just like this one, e.g. in commit d02c357e5b ("KVM: x86/mmu: Retry
  fault before acquiring mmu_lock if mapping is changing").  It'll also
  avoid contentions that may also contribute to a soft-lockup.

  4) Stick with PMD layer simply don't work when PUD is there...  We need
  one way or another to fix PUD mappings on mprotect().

Pushing it to PUD should be the safest approach as of now, e.g. there's yet
no sign of huge P4D coming on any known archs.

Link: https://lkml.kernel.org/r/20240812181225.1360970-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-09-01 20:26:08 -07:00
Zi Yan
2a28713a67 memory tiering: introduce folio_use_access_time() check 
If memory tiering mode is on and a folio is not in the top tier memory,
folio's cpupid field is repurposed to store page access time.  Instead of
an open coded check, use a function to encapsulate the check.

Link: https://lkml.kernel.org/r/20240724130115.793641-3-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-09-01 20:25:47 -07:00
Barry Song
f38ee28519 mm: introduce pmd|pte_needs_soft_dirty_wp helpers for softdirty write-protect 
Patch series "mm: introduce pmd|pte_needs_soft_dirty_wp helpers and
utilize them", v2.


This patchset introduces the pte_need_soft_dirty_wp and
pmd_need_soft_dirty_wp helpers to determine if write protection is
required for softdirty tracking.  These helpers enhance code readability
and improve the overall appearance.

They are then utilized in gup, mprotect, swap, and other related
functions.


This patch (of 2): 

This patch introduces the pte_needs_soft_dirty_wp and
pmd_needs_soft_dirty_wp helpers to determine if write protection is
required for softdirty tracking.  This can enhance code readability and
improve its overall appearance.  These new helpers are then utilized in
gup, huge_memory, and mprotect.

Link: https://lkml.kernel.org/r/20240607211358.4660-1-21cnbao@gmail.com
Link: https://lkml.kernel.org/r/20240607211358.4660-2-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-07-03 19:30:07 -07:00
David Hildenbrand
fce831c920 mm/memory: cleanly support zeropage in vm_insert_page*(), vm_map_pages*() and vmf_insert_mixed() 
For now we only get the (small) zeropage mapped to user space in four
cases (excluding VM_PFNMAP mappings, such as /proc/vmstat):

(1) Read page faults in anonymous VMAs (MAP_PRIVATE|MAP_ANON):
    do_anonymous_page() will not refcount it and map it pte_mkspecial()
(2) UFFDIO_ZEROPAGE on anonymous VMA or COW mapping of shmem
    (MAP_PRIVATE). mfill_atomic_pte_zeropage() will not refcount it and
    map it pte_mkspecial().
(3) KSM in mergeable VMA (anonymous VMA or COW mapping).
    cmp_and_merge_page() will not refcount it and map it
    pte_mkspecial().
(4) FSDAX as an optimization for holes.
    vmf_insert_mixed()->__vm_insert_mixed() might end up calling
    insert_page() without CONFIG_ARCH_HAS_PTE_SPECIAL, refcounting the
    zeropage and not mapping it pte_mkspecial(). With
    CONFIG_ARCH_HAS_PTE_SPECIAL, we'll call insert_pfn() where we will
    not refcount it and map it pte_mkspecial().

In case (4), we might not have VM_MIXEDMAP set: while fs/fuse/dax.c sets
VM_MIXEDMAP, we removed it for ext4 fsdax in commit e1fb4a0864 ("dax:
remove VM_MIXEDMAP for fsdax and device dax") and for XFS in commit
e1fb4a0864 ("dax: remove VM_MIXEDMAP for fsdax and device dax").

Without CONFIG_ARCH_HAS_PTE_SPECIAL and with VM_MIXEDMAP, vm_normal_page()
would currently return the zeropage.  We'll refcount the zeropage when
mapping and when unmapping.

Without CONFIG_ARCH_HAS_PTE_SPECIAL and without VM_MIXEDMAP,
vm_normal_page() would currently refuse to return the zeropage.  So we'd
refcount it when mapping but not when unmapping it ...  do we have fsdax
without CONFIG_ARCH_HAS_PTE_SPECIAL in practice?  Hard to tell.

Independent of that, we should never refcount the zeropage when we might
be holding that reference for a long time, because even without an
accounting imbalance we might overflow the refcount.  As there is interest
in using the zeropage also in other VM_MIXEDMAP mappings, let's add clean
support for that in the cases where it makes sense:

(A) Never refcount the zeropage when mapping it:

In insert_page(), special-case the zeropage, do not refcount it, and use
pte_mkspecial().  Don't involve insert_pfn(), adjusting insert_page()
looks cleaner than branching off to insert_pfn().

(B) Never refcount the zeropage when unmapping it:

In vm_normal_page(), also don't return the zeropage in a VM_MIXEDMAP
mapping without CONFIG_ARCH_HAS_PTE_SPECIAL.  Add a VM_WARN_ON_ONCE()
sanity check if we'd ever return the zeropage, which could happen if
someone forgets to set pte_mkspecial() when mapping the zeropage. 
Document that.

(C) Allow the zeropage only where reasonable

s390x never wants the zeropage in some processes running legacy KVM guests
that make use of storage keys.  So disallow that.

Further, using the zeropage in COW mappings is unproblematic (just what we
do for other COW mappings), because FAULT_FLAG_UNSHARE can just unshare it
and GUP with FOLL_LONGTERM would work as expected.

Similarly, mappings that can never have writable PTEs (implying no write
faults) are also not problematic, because nothing could end up mapping the
PTE writable by mistake later.  But in case we could have writable PTEs,
we'll only allow the zeropage in FSDAX VMAs, that are incompatible with
GUP and are blocked there completely.

We'll always require the zeropage to be mapped with pte_special(). 
GUP-fast will reject the zeropage that way, but GUP-slow will allow it. 
(Note that GUP does not refcount the zeropage with FOLL_PIN, because there
were issues with overflowing the refcount in the past).

Add sanity checks to can_change_pte_writable() and wp_page_reuse(), to
catch early during testing if we'd ever find a zeropage unexpectedly in
code that wants to upgrade write permissions.

Convert the BUG_ON in vm_mixed_ok() to an ordinary check and simply fail
with VM_FAULT_SIGBUS, like we do for other sanity checks.  Drop the stale
comment regarding reserved pages from insert_page().

Note that:
* we won't mess with VM_PFNMAP mappings for now. remap_pfn_range() and
  vmf_insert_pfn() would allow the zeropage in some cases and
  not refcount it.
* vmf_insert_pfn*() will reject the zeropage in VM_MIXEDMAP
  mappings and we'll leave that alone for now. People can simply use
  one of the other interfaces.
* we won't bother with the huge zeropage for now. It's never
  PTE-mapped and also GUP does not special-case it yet.

Link: https://lkml.kernel.org/r/20240522125713.775114-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-07-03 19:29:56 -07:00
Jeff Xu
8be7258aad mseal: add mseal syscall 
The new mseal() is an syscall on 64 bit CPU, and with following signature:

int mseal(void addr, size_t len, unsigned long flags)
addr/len: memory range.
flags: reserved.

mseal() blocks following operations for the given memory range.

1> Unmapping, moving to another location, and shrinking the size,
   via munmap() and mremap(), can leave an empty space, therefore can
   be replaced with a VMA with a new set of attributes.

2> Moving or expanding a different VMA into the current location,
   via mremap().

3> Modifying a VMA via mmap(MAP_FIXED).

4> Size expansion, via mremap(), does not appear to pose any specific
   risks to sealed VMAs. It is included anyway because the use case is
   unclear. In any case, users can rely on merging to expand a sealed VMA.

5> mprotect() and pkey_mprotect().

6> Some destructive madvice() behaviors (e.g. MADV_DONTNEED) for anonymous
   memory, when users don't have write permission to the memory. Those
   behaviors can alter region contents by discarding pages, effectively a
   memset(0) for anonymous memory.

Following input during RFC are incooperated into this patch:

Jann Horn: raising awareness and providing valuable insights on the
destructive madvise operations.
Linus Torvalds: assisting in defining system call signature and scope.
Liam R. Howlett: perf optimization.
Theo de Raadt: sharing the experiences and insight gained from
  implementing mimmutable() in OpenBSD.

Finally, the idea that inspired this patch comes from Stephen Röttger's
work in Chrome V8 CFI.

[jeffxu@chromium.org: add branch prediction hint, per Pedro]
  Link: https://lkml.kernel.org/r/20240423192825.1273679-2-jeffxu@chromium.org
Link: https://lkml.kernel.org/r/20240415163527.626541-3-jeffxu@chromium.org
Signed-off-by: Jeff Xu <jeffxu@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Pedro Falcato <pedro.falcato@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Jann Horn <jannh@google.com>
Cc: Jeff Xu <jeffxu@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jorge Lucangeli Obes <jorgelo@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Pedro Falcato <pedro.falcato@gmail.com>
Cc: Stephen Röttger <sroettger@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Amer Al Shanawany <amer.shanawany@gmail.com>
Cc: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-05-23 19:40:26 -07:00
Baolin Wang
d2136d749d mm: support multi-size THP numa balancing 
Now the anonymous page allocation already supports multi-size THP (mTHP),
but the numa balancing still prohibits mTHP migration even though it is an
exclusive mapping, which is unreasonable.

Allow scanning mTHP:
Commit 859d4adc34 ("mm: numa: do not trap faults on shared data section
pages") skips shared CoW pages' NUMA page migration to avoid shared data
segment migration. In addition, commit 80d47f5de5 ("mm: don't try to
NUMA-migrate COW pages that have other uses") change to use page_count()
to avoid GUP pages migration, that will also skip the mTHP numa scanning.
Theoretically, we can use folio_maybe_dma_pinned() to detect the GUP
issue, although there is still a GUP race, the issue seems to have been
resolved by commit 80d47f5de5. Meanwhile, use the folio_likely_mapped_shared()
to skip shared CoW pages though this is not a precise sharers count. To
check if the folio is shared, ideally we want to make sure every page is
mapped to the same process, but doing that seems expensive and using
the estimated mapcount seems can work when running autonuma benchmark.

Allow migrating mTHP:
As mentioned in the previous thread[1], large folios (including THP) are
more susceptible to false sharing issues among threads than 4K base page,
leading to pages ping-pong back and forth during numa balancing, which is
currently not easy to resolve. Therefore, as a start to support mTHP numa
balancing, we can follow the PMD mapped THP's strategy, that means we can
reuse the 2-stage filter in should_numa_migrate_memory() to check if the
mTHP is being heavily contended among threads (through checking the CPU id
and pid of the last access) to avoid false sharing at some degree. Thus,
we can restore all PTE maps upon the first hint page fault of a large folio
to follow the PMD mapped THP's strategy. In the future, we can continue to
optimize the NUMA balancing algorithm to avoid the false sharing issue with
large folios as much as possible.

Performance data:
Machine environment: 2 nodes, 128 cores Intel(R) Xeon(R) Platinum
Base: 2024-03-25 mm-unstable branch
Enable mTHP to run autonuma-benchmark

mTHP:16K
Base				Patched
numa01				numa01
224.70				143.48
numa01_THREAD_ALLOC		numa01_THREAD_ALLOC
118.05				47.43
numa02				numa02
13.45				9.29
numa02_SMT			numa02_SMT
14.80				7.50

mTHP:64K
Base				Patched
numa01				numa01
216.15				114.40
numa01_THREAD_ALLOC		numa01_THREAD_ALLOC
115.35				47.41
numa02				numa02
13.24				9.25
numa02_SMT			numa02_SMT
14.67				7.34

mTHP:128K
Base				Patched
numa01				numa01
205.13				144.45
numa01_THREAD_ALLOC		numa01_THREAD_ALLOC
112.93				41.88
numa02				numa02
13.16				9.18
numa02_SMT			numa02_SMT
14.81				7.49

[1] https://lore.kernel.org/all/20231117100745.fnpijbk4xgmals3k@techsingularity.net/

[baolin.wang@linux.alibaba.com: v3]
  Link: https://lkml.kernel.org/r/c33a5c0b0a0323b1f8ed53772f50501f4b196e25.1712132950.git.baolin.wang@linux.alibaba.com
Link: https://lkml.kernel.org/r/d28d276d599c26df7f38c9de8446f60e22dd1950.1711683069.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-04-25 20:56:30 -07:00
Matthew Wilcox (Oracle)
f2d571b0b2 mprotect: use pfn_swap_entry_folio 
We only want to know whether the folio is anonymous, so use
pfn_swap_entry_folio() and save a call to compound_head().

Link: https://lkml.kernel.org/r/20240111152429.3374566-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-02-21 16:00:03 -08:00
Kefeng Wang
ec1778807a mm: mprotect: use a folio in change_pte_range() 
Use a folio in change_pte_range() to save three compound_head() calls.
Since now only normal and PMD-mapped page is handled by numa balancing,
it is enough to only update the entire folio's access time.

Link: https://lkml.kernel.org/r/20231018140806.2783514-10-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-10-25 16:47:12 -07:00
Lorenzo Stoakes
94d7d92339 mm: abstract the vma_merge()/split_vma() pattern for mprotect() et al. 
mprotect() and other functions which change VMA parameters over a range
each employ a pattern of:-

1. Attempt to merge the range with adjacent VMAs.
2. If this fails, and the range spans a subset of the VMA, split it
   accordingly.

This is open-coded and duplicated in each case. Also in each case most of
the parameters passed to vma_merge() remain the same.

Create a new function, vma_modify(), which abstracts this operation,
accepting only those parameters which can be changed.

To avoid the mess of invoking each function call with unnecessary
parameters, create inline wrapper functions for each of the modify
operations, parameterised only by what is required to perform the action.

We can also significantly simplify the logic - by returning the VMA if we
split (or merged VMA if we do not) we no longer need specific handling for
merge/split cases in any of the call sites.

Note that the userfaultfd_release() case works even though it does not
split VMAs - since start is set to vma->vm_start and end is set to
vma->vm_end, the split logic does not trigger.

In addition, since we calculate pgoff to be equal to vma->vm_pgoff + (start
- vma->vm_start) >> PAGE_SHIFT, and start - vma->vm_start will be 0 in this
instance, this invocation will remain unchanged.

We eliminate a VM_WARN_ON() in mprotect_fixup() as this simply asserts that
vma_merge() correctly ensures that flags remain the same, something that is
already checked in is_mergeable_vma() and elsewhere, and in any case is not
specific to mprotect().

Link: https://lkml.kernel.org/r/0dfa9368f37199a423674bf0ee312e8ea0619044.1697043508.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-10-18 14:34:18 -07:00
Lorenzo Stoakes
9b91432985 mm/mprotect: allow unfaulted VMAs to be unaccounted on mprotect() 
When mprotect() is used to make unwritable VMAs writable, they have the
VM_ACCOUNT flag applied and memory accounted accordingly.

If the VMA has had no pages faulted in and is then made unwritable once
again, it will remain accounted for, despite not being capable of
extending memory usage.

Consider:-

ptr = mmap(NULL, page_size * 3, PROT_READ, MAP_ANON | MAP_PRIVATE, -1, 0);
mprotect(ptr + page_size, page_size, PROT_READ | PROT_WRITE);
mprotect(ptr + page_size, page_size, PROT_READ);

The first mprotect() splits the range into 3 VMAs and the second fails to
merge the three as the middle VMA has VM_ACCOUNT set and the others do
not, rendering them unmergeable.

This is unnecessary, since no pages have actually been allocated and the
middle VMA is not capable of utilising more memory, thereby introducing
unnecessary VMA fragmentation (and accounting for more memory than is
necessary).

Since we cannot efficiently determine which pages map to an anonymous VMA,
we have to be very conservative - determining whether any pages at all
have been faulted in, by checking whether vma->anon_vma is NULL.

We can see that the lack of anon_vma implies that no anonymous pages are
present as evidenced by vma_needs_copy() utilising this on fork to
determine whether page tables need to be copied.

The only place where anon_vma is set NULL explicitly is on fork with
VM_WIPEONFORK set, however since this flag is intended to cause the child
process to not CoW on a given memory range, it is right to interpret this
as indicating the VMA has no faulted-in anonymous memory mapped.

If the VMA was forked without VM_WIPEONFORK set, then anon_vma_fork() will
have ensured that a new anon_vma is assigned (and correctly related to its
parent anon_vma) should any pages be CoW-mapped.

The overall operation is safe against races as we hold a write lock against
mm->mmap_lock.

If we could efficiently look up the VMA's faulted-in pages then we would
unaccount all those pages not yet faulted in.  However as the original
comment alludes this simply isn't currently possible, so we are
conservative and account all pages or none at all.

Link: https://lkml.kernel.org/r/ad5540371a16623a069f03f4db1739f33cde1fab.1696921767.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-10-18 14:34:18 -07:00
Linus Torvalds
df57721f9a Add x86 shadow stack support 
Convert IBT selftest to asm to fix objtool warning
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Merge tag 'x86_shstk_for_6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 shadow stack support from Dave Hansen:
 "This is the long awaited x86 shadow stack support, part of Intel's
  Control-flow Enforcement Technology (CET).

  CET consists of two related security features: shadow stacks and
  indirect branch tracking. This series implements just the shadow stack
  part of this feature, and just for userspace.

  The main use case for shadow stack is providing protection against
  return oriented programming attacks. It works by maintaining a
  secondary (shadow) stack using a special memory type that has
  protections against modification. When executing a CALL instruction,
  the processor pushes the return address to both the normal stack and
  to the special permission shadow stack. Upon RET, the processor pops
  the shadow stack copy and compares it to the normal stack copy.

  For more information, refer to the links below for the earlier
  versions of this patch set"

Link: https://lore.kernel.org/lkml/20220130211838.8382-1-rick.p.edgecombe@intel.com/
Link: https://lore.kernel.org/lkml/20230613001108.3040476-1-rick.p.edgecombe@intel.com/

* tag 'x86_shstk_for_6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (47 commits)
  x86/shstk: Change order of __user in type
  x86/ibt: Convert IBT selftest to asm
  x86/shstk: Don't retry vm_munmap() on -EINTR
  x86/kbuild: Fix Documentation/ reference
  x86/shstk: Move arch detail comment out of core mm
  x86/shstk: Add ARCH_SHSTK_STATUS
  x86/shstk: Add ARCH_SHSTK_UNLOCK
  x86: Add PTRACE interface for shadow stack
  selftests/x86: Add shadow stack test
  x86/cpufeatures: Enable CET CR4 bit for shadow stack
  x86/shstk: Wire in shadow stack interface
  x86: Expose thread features in /proc/$PID/status
  x86/shstk: Support WRSS for userspace
  x86/shstk: Introduce map_shadow_stack syscall
  x86/shstk: Check that signal frame is shadow stack mem
  x86/shstk: Check that SSP is aligned on sigreturn
  x86/shstk: Handle signals for shadow stack
  x86/shstk: Introduce routines modifying shstk
  x86/shstk: Handle thread shadow stack
  x86/shstk: Add user-mode shadow stack support
  ...
 2023-08-31 12:20:12 -07:00
Andrew Morton
5994eabf3b merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes 2023-08-21 14:26:20 -07:00
Suren Baghdasaryan
60081bf19b mm: lock vma explicitly before doing vm_flags_reset and vm_flags_reset_once 
Implicit vma locking inside vm_flags_reset() and vm_flags_reset_once() is
not obvious and makes it hard to understand where vma locking is happening.
Also in some cases (like in dup_userfaultfd()) vma should be locked earlier
than vma_flags modification. To make locking more visible, change these
functions to assert that the vma write lock is taken and explicitly lock
the vma beforehand. Fix userfaultfd functions which should lock the vma
earlier.

Link: https://lkml.kernel.org/r/20230804152724.3090321-5-surenb@google.com
Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-08-21 13:37:46 -07:00
Suren Baghdasaryan
49b0638502 mm: enable page walking API to lock vmas during the walk 
walk_page_range() and friends often operate under write-locked mmap_lock. 
With introduction of vma locks, the vmas have to be locked as well during
such walks to prevent concurrent page faults in these areas.  Add an
additional member to mm_walk_ops to indicate locking requirements for the
walk.

The change ensures that page walks which prevent concurrent page faults
by write-locking mmap_lock, operate correctly after introduction of
per-vma locks.  With per-vma locks page faults can be handled under vma
lock without taking mmap_lock at all, so write locking mmap_lock would
not stop them.  The change ensures vmas are properly locked during such
walks.

A sample issue this solves is do_mbind() performing queue_pages_range()
to queue pages for migration.  Without this change a concurrent page
can be faulted into the area and be left out of migration.

Link: https://lkml.kernel.org/r/20230804152724.3090321-2-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Suggested-by: Jann Horn <jannh@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michel Lespinasse <michel@lespinasse.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-08-21 13:07:20 -07:00
Miaohe Lin
eafcb7a972 mm/mprotect: fix obsolete function name in change_pte_range() 
Since commit 79a1971c5f ("mm: move the copy_one_pte() pte_present check
into the caller"), the explanation of preserving soft-dirtiness is moved
into copy_nonpresent_pte().  Update corresponding comment.

Link: https://lkml.kernel.org/r/20230723033114.3224409-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-08-18 10:12:43 -07:00
Axel Rasmussen
af19487f00 mm: make PTE_MARKER_SWAPIN_ERROR more general 
Patch series "add UFFDIO_POISON to simulate memory poisoning with UFFD",
v4.

This series adds a new userfaultfd feature, UFFDIO_POISON. See commit 4
for a detailed description of the feature.


This patch (of 8):

Future patches will reuse PTE_MARKER_SWAPIN_ERROR to implement
UFFDIO_POISON, so make some various preparations for that:

First, rename it to just PTE_MARKER_POISONED.  The "SWAPIN" can be
confusing since we're going to re-use it for something not really related
to swap.  This can be particularly confusing for things like hugetlbfs,
which doesn't support swap whatsoever.  Also rename some various helper
functions.

Next, fix pte marker copying for hugetlbfs.  Previously, it would WARN on
seeing a PTE_MARKER_SWAPIN_ERROR, since hugetlbfs doesn't support swap. 
But, since we're going to re-use it, we want it to go ahead and copy it
just like non-hugetlbfs memory does today.  Since the code to do this is
more complicated now, pull it out into a helper which can be re-used in
both places.  While we're at it, also make it slightly more explicit in
its handling of e.g.  uffd wp markers.

For non-hugetlbfs page faults, instead of returning VM_FAULT_SIGBUS for an
error entry, return VM_FAULT_HWPOISON.  For most cases this change doesn't
matter, e.g.  a userspace program would receive a SIGBUS either way.  But
for UFFDIO_POISON, this change will let KVM guests get an MCE out of the
box, instead of giving a SIGBUS to the hypervisor and requiring it to
somehow inject an MCE.

Finally, for hugetlbfs faults, handle PTE_MARKER_POISONED, and return
VM_FAULT_HWPOISON_LARGE in such cases.  Note that this can't happen today
because the lack of swap support means we'll never end up with such a PTE
anyway, but this behavior will be needed once such entries *can* show up
via UFFDIO_POISON.

Link: https://lkml.kernel.org/r/20230707215540.2324998-1-axelrasmussen@google.com
Link: https://lkml.kernel.org/r/20230707215540.2324998-2-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gaosheng Cui <cuigaosheng1@huawei.com>
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jan Alexander Steffens (heftig) <heftig@archlinux.org>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nadav Amit <namit@vmware.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: T.J. Alumbaugh <talumbau@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: ZhangPeng <zhangpeng362@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-08-18 10:12:16 -07:00
Rick Edgecombe
161e393c0f mm: Make pte_mkwrite() take a VMA 
The x86 Shadow stack feature includes a new type of memory called shadow
stack. This shadow stack memory has some unusual properties, which requires
some core mm changes to function properly.

One of these unusual properties is that shadow stack memory is writable,
but only in limited ways. These limits are applied via a specific PTE
bit combination. Nevertheless, the memory is writable, and core mm code
will need to apply the writable permissions in the typical paths that
call pte_mkwrite(). Future patches will make pte_mkwrite() take a VMA, so
that the x86 implementation of it can know whether to create regular
writable or shadow stack mappings.

But there are a couple of challenges to this. Modifying the signatures of
each arch pte_mkwrite() implementation would be error prone because some
are generated with macros and would need to be re-implemented. Also, some
pte_mkwrite() callers operate on kernel memory without a VMA.

So this can be done in a three step process. First pte_mkwrite() can be
renamed to pte_mkwrite_novma() in each arch, with a generic pte_mkwrite()
added that just calls pte_mkwrite_novma(). Next callers without a VMA can
be moved to pte_mkwrite_novma(). And lastly, pte_mkwrite() and all callers
can be changed to take/pass a VMA.

Previous work pte_mkwrite() renamed pte_mkwrite_novma() and converted
callers that don't have a VMA were to use pte_mkwrite_novma(). So now
change pte_mkwrite() to take a VMA and change the remaining callers to
pass a VMA. Apply the same changes for pmd_mkwrite().

No functional change.

Suggested-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/all/20230613001108.3040476-4-rick.p.edgecombe%40intel.com
 2023-07-11 14:12:15 -07:00
Andrew Morton
63773d2b59 Merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes. 2023-06-23 16:58:19 -07:00
Ryan Roberts
c33c794828 mm: ptep_get() conversion 
Convert all instances of direct pte_t* dereferencing to instead use
ptep_get() helper.  This means that by default, the accesses change from a
C dereference to a READ_ONCE().  This is technically the correct thing to
do since where pgtables are modified by HW (for access/dirty) they are
volatile and therefore we should always ensure READ_ONCE() semantics.

But more importantly, by always using the helper, it can be overridden by
the architecture to fully encapsulate the contents of the pte.  Arch code
is deliberately not converted, as the arch code knows best.  It is
intended that arch code (arm64) will override the default with its own
implementation that can (e.g.) hide certain bits from the core code, or
determine young/dirty status by mixing in state from another source.

Conversion was done using Coccinelle:

----

// $ make coccicheck \
//          COCCI=ptepget.cocci \
//          SPFLAGS="--include-headers" \
//          MODE=patch

virtual patch

@ depends on patch @
pte_t *v;
@@

- *v
+ ptep_get(v)

----

Then reviewed and hand-edited to avoid multiple unnecessary calls to
ptep_get(), instead opting to store the result of a single call in a
variable, where it is correct to do so.  This aims to negate any cost of
READ_ONCE() and will benefit arch-overrides that may be more complex.

Included is a fix for an issue in an earlier version of this patch that
was pointed out by kernel test robot.  The issue arose because config
MMU=n elides definition of the ptep helper functions, including
ptep_get().  HUGETLB_PAGE=n configs still define a simple
huge_ptep_clear_flush() for linking purposes, which dereferences the ptep.
So when both configs are disabled, this caused a build error because
ptep_get() is not defined.  Fix by continuing to do a direct dereference
when MMU=n.  This is safe because for this config the arch code cannot be
trying to virtualize the ptes because none of the ptep helpers are
defined.

Link: https://lkml.kernel.org/r/20230612151545.3317766-4-ryan.roberts@arm.com
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202305120142.yXsNEo6H-lkp@intel.com/
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Dimitri Sivanich <dimitri.sivanich@hpe.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-06-19 16:19:25 -07:00
Hugh Dickins
670ddd8cdc mm/mprotect: delete pmd_none_or_clear_bad_unless_trans_huge() 
change_pmd_range() had special pmd_none_or_clear_bad_unless_trans_huge(),
required to avoid "bad" choices when setting automatic NUMA hinting under
mmap_read_lock(); but most of that is already covered in pte_offset_map()
now.  change_pmd_range() just wants a pmd_none() check before wasting time
on MMU notifiers, then checks on the read-once _pmd value to work out
what's needed for huge cases.  If change_pte_range() returns -EAGAIN to
retry if pte_offset_map_lock() fails, nothing more special is needed.

Link: https://lkml.kernel.org/r/725a42a9-91e9-c868-925-e3a5fd40bb4f@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <song@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zack Rusin <zackr@vmware.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-06-19 16:19:16 -07:00
Hugh Dickins
26e1a0c327 mm: use pmdp_get_lockless() without surplus barrier() 
Patch series "mm: allow pte_offset_map[_lock]() to fail", v2.

What is it all about?  Some mmap_lock avoidance i.e.  latency reduction. 
Initially just for the case of collapsing shmem or file pages to THPs; but
likely to be relied upon later in other contexts e.g.  freeing of empty
page tables (but that's not work I'm doing).  mmap_write_lock avoidance
when collapsing to anon THPs?  Perhaps, but again that's not work I've
done: a quick attempt was not as easy as the shmem/file case.

I would much prefer not to have to make these small but wide-ranging
changes for such a niche case; but failed to find another way, and have
heard that shmem MADV_COLLAPSE's usefulness is being limited by that
mmap_write_lock it currently requires.

These changes (though of course not these exact patches) have been in
Google's data centre kernel for three years now: we do rely upon them.

What is this preparatory series about?

The current mmap locking will not be enough to guard against that tricky
transition between pmd entry pointing to page table, and empty pmd entry,
and pmd entry pointing to huge page: pte_offset_map() will have to
validate the pmd entry for itself, returning NULL if no page table is
there.  What to do about that varies: sometimes nearby error handling
indicates just to skip it; but in many cases an ACTION_AGAIN or "goto
again" is appropriate (and if that risks an infinite loop, then there must
have been an oops, or pfn 0 mistaken for page table, before).

Given the likely extension to freeing empty page tables, I have not
limited this set of changes to a THP config; and it has been easier, and
sets a better example, if each site is given appropriate handling: even
where deeper study might prove that failure could only happen if the pmd
table were corrupted.

Several of the patches are, or include, cleanup on the way; and by the
end, pmd_trans_unstable() and suchlike are deleted: pte_offset_map() and
pte_offset_map_lock() then handle those original races and more.  Most
uses of pte_lockptr() are deprecated, with pte_offset_map_nolock() taking
its place.


This patch (of 32):

Use pmdp_get_lockless() in preference to READ_ONCE(*pmdp), to get a more
reliable result with PAE (or READ_ONCE as before without PAE); and remove
the unnecessary extra barrier()s which got left behind in its callers.

HOWEVER: Note the small print in linux/pgtable.h, where it was designed
specifically for fast GUP, and depends on interrupts being disabled for
its full guarantee: most callers which have been added (here and before)
do NOT have interrupts disabled, so there is still some need for caution.

Link: https://lkml.kernel.org/r/f35279a9-9ac0-de22-d245-591afbfb4dc@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Yu Zhao <yuzhao@google.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <song@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zack Rusin <zackr@vmware.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-06-19 16:19:12 -07:00
Liam R. Howlett
77795f900e mm/mprotect: fix do_mprotect_pkey() limit check 
The return of do_mprotect_pkey() can still be incorrectly returned as
success if there is a gap that spans to or beyond the end address passed
in.  Update the check to ensure that the end address has indeed been seen.

Link: https://lore.kernel.org/all/CABi2SkXjN+5iFoBhxk71t3cmunTk-s=rB4T7qo0UQRh17s49PQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20230606182912.586576-1-Liam.Howlett@oracle.com
Fixes: 82f951340f ("mm/mprotect: fix do_mprotect_pkey() return on error")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: Jeff Xu <jeffxu@chromium.org>
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-06-19 13:19:31 -07:00
David Hildenbrand
27da93d8e6 mm/userfaultfd: don't consider uffd-wp bit of writable migration entries 
If we end up with a writable migration entry that has the uffd-wp bit set,
we already messed up: the source PTE/PMD was writable, which means we
could have modified the page without notifying uffd first.  Setting the
uffd-wp bit always implies converting migration entries to !writable
migration entries.

Commit 8f34f1eac3 ("mm/userfaultfd: fix uffd-wp special cases for
fork()") documents that "3.  Forget to carry over uffd-wp bit for a write
migration huge pmd entry", but it doesn't really say why that should be
relevant.

So let's remove that code to avoid hiding an eventual underlying issue (in
the future, we might want to warn when creating writable migration entries
that have the uffd-wp bit set -- or even better when turning a PTE
writable that still has the uffd-wp bit set).

This now matches the handling for hugetlb migration entries in
hugetlb_change_protection().

In copy_huge_pmd()/copy_nonpresent_pte()/copy_hugetlb_page_range(), we
still transfer the uffd-bit also for writable migration entries, but
simply because we have unified handling for "writable" and
"readable-exclusive" migration entries, and we care about transferring the
uffd-wp bit for the latter.

Link: https://lkml.kernel.org/r/20230405160236.587705-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-04-18 16:29:53 -07:00
Andrew Morton
e492cd61b9 sync mm-stable with mm-hotfixes-stable to pick up depended-upon upstream changes 2023-04-16 12:31:58 -07:00
Liam R. Howlett
82f951340f mm/mprotect: fix do_mprotect_pkey() return on error 
When the loop over the VMA is terminated early due to an error, the return
code could be overwritten with ENOMEM.  Fix the return code by only
setting the error on early loop termination when the error is not set.

User-visible effects include: attempts to run mprotect() against a
special mapping or with a poorly-aligned hugetlb address should return
-EINVAL, but they presently return -ENOMEM.  In other cases an -EACCESS
should be returned.

Link: https://lkml.kernel.org/r/20230406193050.1363476-1-Liam.Howlett@oracle.com
Fixes: 2286a6914c ("mm: change mprotect_fixup to vma iterator")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-04-16 10:41:24 -07:00
Peter Xu
2bad466cc9 mm/uffd: UFFD_FEATURE_WP_UNPOPULATED 
Patch series "mm/uffd: Add feature bit UFFD_FEATURE_WP_UNPOPULATED", v4.

The new feature bit makes anonymous memory acts the same as file memory on
userfaultfd-wp in that it'll also wr-protect none ptes.

It can be useful in two cases:

(1) Uffd-wp app that needs to wr-protect none ptes like QEMU snapshot,
    so pre-fault can be replaced by enabling this flag and speed up
    protections

(2) It helps to implement async uffd-wp mode that Muhammad is working on [1]

It's debatable whether this is the most ideal solution because with the
new feature bit set, wr-protect none pte needs to pre-populate the
pgtables to the last level (PAGE_SIZE).  But it seems fine so far to
service either purpose above, so we can leave optimizations for later.

The series brings pte markers to anonymous memory too.  There's some
change in the common mm code path in the 1st patch, great to have some eye
looking at it, but hopefully they're still relatively straightforward.


This patch (of 2):

This is a new feature that controls how uffd-wp handles none ptes.  When
it's set, the kernel will handle anonymous memory the same way as file
memory, by allowing the user to wr-protect unpopulated ptes.

File memories handles none ptes consistently by allowing wr-protecting of
none ptes because of the unawareness of page cache being exist or not. 
For anonymous it was not as persistent because we used to assume that we
don't need protections on none ptes or known zero pages.

One use case of such a feature bit was VM live snapshot, where if without
wr-protecting empty ptes the snapshot can contain random rubbish in the
holes of the anonymous memory, which can cause misbehave of the guest when
the guest OS assumes the pages should be all zeros.

QEMU worked it around by pre-populate the section with reads to fill in
zero page entries before starting the whole snapshot process [1].

Recently there's another need raised on using userfaultfd wr-protect for
detecting dirty pages (to replace soft-dirty in some cases) [2].  In that
case if without being able to wr-protect none ptes by default, the dirty
info can get lost, since we cannot treat every none pte to be dirty (the
current design is identify a page dirty based on uffd-wp bit being
cleared).

In general, we want to be able to wr-protect empty ptes too even for
anonymous.

This patch implements UFFD_FEATURE_WP_UNPOPULATED so that it'll make
uffd-wp handling on none ptes being consistent no matter what the memory
type is underneath.  It doesn't have any impact on file memories so far
because we already have pte markers taking care of that.  So it only
affects anonymous.

The feature bit is by default off, so the old behavior will be maintained.
Sometimes it may be wanted because the wr-protect of none ptes will
contain overheads not only during UFFDIO_WRITEPROTECT (by applying pte
markers to anonymous), but also on creating the pgtables to store the pte
markers.  So there's potentially less chance of using thp on the first
fault for a none pmd or larger than a pmd.

The major implementation part is teaching the whole kernel to understand
pte markers even for anonymously mapped ranges, meanwhile allowing the
UFFDIO_WRITEPROTECT ioctl to apply pte markers for anonymous too when the
new feature bit is set.

Note that even if the patch subject starts with mm/uffd, there're a few
small refactors to major mm path of handling anonymous page faults.  But
they should be straightforward.

With WP_UNPOPUATED, application like QEMU can avoid pre-read faults all
the memory before wr-protect during taking a live snapshot.  Quotting from
Muhammad's test result here [3] based on a simple program [4]:

  (1) With huge page disabled
  echo madvise > /sys/kernel/mm/transparent_hugepage/enabled
  ./uffd_wp_perf
  Test DEFAULT: 4
  Test PRE-READ: 1111453 (pre-fault 1101011)
  Test MADVISE: 278276 (pre-fault 266378)
  Test WP-UNPOPULATE: 11712

  (2) With Huge page enabled
  echo always > /sys/kernel/mm/transparent_hugepage/enabled
  ./uffd_wp_perf
  Test DEFAULT: 4
  Test PRE-READ: 22521 (pre-fault 22348)
  Test MADVISE: 4909 (pre-fault 4743)
  Test WP-UNPOPULATE: 14448

There'll be a great perf boost for no-thp case, while for thp enabled with
extreme case of all-thp-zero WP_UNPOPULATED can be slower than MADVISE,
but that's low possibility in reality, also the overhead was not reduced
but postponed until a follow up write on any huge zero thp, so potentially
it is faster by making the follow up writes slower.

[1] https://lore.kernel.org/all/20210401092226.102804-4-andrey.gruzdev@virtuozzo.com/
[2] https://lore.kernel.org/all/Y+v2HJ8+3i%2FKzDBu@x1n/
[3] https://lore.kernel.org/all/d0eb0a13-16dc-1ac1-653a-78b7273781e3@collabora.com/
[4] https://github.com/xzpeter/clibs/blob/master/uffd-test/uffd-wp-perf.c

[peterx@redhat.com: comment changes, oneliner fix to khugepaged]
  Link: https://lkml.kernel.org/r/ZB2/8jPhD3fpx5U8@x1n
Link: https://lkml.kernel.org/r/20230309223711.823547-1-peterx@redhat.com
Link: https://lkml.kernel.org/r/20230309223711.823547-2-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Paul Gofman <pgofman@codeweavers.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-04-05 19:42:44 -07:00
Joey Gouly
3d27a95b1d mm: fix error handling for map_deny_write_exec 
Commit 4a18419f71 ("mm/mprotect: use mmu_gather") changed 'goto out;' to
'break' in the loop.

This wasn't noticed while rebasing the MDWE patches, so fix it now.

Link: https://lkml.kernel.org/r/20230308190423.46491-3-joey.gouly@arm.com
Fixes: b507808ebc ("mm: implement memory-deny-write-execute as a prctl")
Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Reported-by: Alexey Izbyshev <izbyshev@ispras.ru>
  Link: https://lore.kernel.org/linux-arm-kernel/8408d8901e9d7ee6b78db4c6cba04b78@ispras.ru/
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: nd <nd@arm.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-03-23 17:18:33 -07:00
Liam R. Howlett
2fcd07b7cc mm/mprotect: Fix successful vma_merge() of next in do_mprotect_pkey() 
If mprotect_fixup() successfully calls vma_merge() and replaces vma and
the next vma, then the tmp variable in the do_mprotect_pkey() is not
updated to point to the new vma end.  This results in the loop detecting
a gap between VMAs that does not exist.

Fix the faulty value of tmp by setting it to the end location of the vma
iterator at the end of the loop.

Link: https://lkml.kernel.org/r/20230224212055.1786100-1-Liam.Howlett@oracle.com
Fixes: 2286a6914c ("mm: change mprotect_fixup to vma iterator")
Link: https://lore.kernel.org/linux-mm/20230223120407.729110a6ecd1416ac59d9cb0@linux-foundation.org/
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: Bert Karwatzki <spasswolf@web.de>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217061
Tested-by: Bert Karwatzki <spasswolf@web.de>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/linux-mm/CAHk-=wjFmVL7NiuxL54qLkoabni_yD-oF9=dpDgETtdsiCbhUg@mail.gmail.com/
Tested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2023-02-25 20:16:48 -08:00
Suren Baghdasaryan
1c71222e5f mm: replace vma->vm_flags direct modifications with modifier calls 
Replace direct modifications to vma->vm_flags with calls to modifier
functions to be able to track flag changes and to keep vma locking
correctness.

[akpm@linux-foundation.org: fix drivers/misc/open-dice.c, per Hyeonggon Yoo]
Link: https://lkml.kernel.org/r/20230126193752.297968-5-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjun Roy <arjunroy@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Minchan Kim <minchan@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Oskolkov <posk@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Punit Agrawal <punit.agrawal@bytedance.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-02-09 16:51:39 -08:00
Liam R. Howlett
9760ebffbf mm: switch vma_merge(), split_vma(), and __split_vma to vma iterator 
Drop the vmi_* functions and transition all users to use the vma iterator
directly.

Link: https://lkml.kernel.org/r/20230120162650.984577-30-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-02-09 16:51:35 -08:00
Liam R. Howlett
2286a6914c mm: change mprotect_fixup to vma iterator 
Use the vma iterator so that the iterator can be invalidated or updated to
avoid each caller doing so.

Link: https://lkml.kernel.org/r/20230120162650.984577-18-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-02-09 16:51:33 -08:00
Joey Gouly
b507808ebc mm: implement memory-deny-write-execute as a prctl 
Patch series "mm: In-kernel support for memory-deny-write-execute (MDWE)",
v2.

The background to this is that systemd has a configuration option called
MemoryDenyWriteExecute [2], implemented as a SECCOMP BPF filter.  Its aim
is to prevent a user task from inadvertently creating an executable
mapping that is (or was) writeable.  Since such BPF filter is stateless,
it cannot detect mappings that were previously writeable but subsequently
changed to read-only.  Therefore the filter simply rejects any
mprotect(PROT_EXEC).  The side-effect is that on arm64 with BTI support
(Branch Target Identification), the dynamic loader cannot change an ELF
section from PROT_EXEC to PROT_EXEC|PROT_BTI using mprotect().  For
libraries, it can resort to unmapping and re-mapping but for the main
executable it does not have a file descriptor.  The original bug report in
the Red Hat bugzilla - [3] - and subsequent glibc workaround for libraries
- [4].

This series adds in-kernel support for this feature as a prctl
PR_SET_MDWE, that is inherited on fork().  The prctl denies PROT_WRITE |
PROT_EXEC mappings.  Like the systemd BPF filter it also denies adding
PROT_EXEC to mappings.  However unlike the BPF filter it only denies it if
the mapping didn't previous have PROT_EXEC.  This allows to PROT_EXEC ->
PROT_EXEC | PROT_BTI with mprotect(), which is a problem with the BPF
filter.


This patch (of 2):

The aim of such policy is to prevent a user task from creating an
executable mapping that is also writeable.

An example of mmap() returning -EACCESS if the policy is enabled:

	mmap(0, size, PROT_READ | PROT_WRITE | PROT_EXEC, flags, 0, 0);

Similarly, mprotect() would return -EACCESS below:

	addr = mmap(0, size, PROT_READ | PROT_EXEC, flags, 0, 0);
	mprotect(addr, size, PROT_READ | PROT_WRITE | PROT_EXEC);

The BPF filter that systemd MDWE uses is stateless, and disallows
mprotect() with PROT_EXEC completely. This new prctl allows PROT_EXEC to
be enabled if it was already PROT_EXEC, which allows the following case:

	addr = mmap(0, size, PROT_READ | PROT_EXEC, flags, 0, 0);
	mprotect(addr, size, PROT_READ | PROT_EXEC | PROT_BTI);

where PROT_BTI enables branch tracking identification on arm64.

Link: https://lkml.kernel.org/r/20230119160344.54358-1-joey.gouly@arm.com
Link: https://lkml.kernel.org/r/20230119160344.54358-2-joey.gouly@arm.com
Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Co-developed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jeremy Linton <jeremy.linton@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Mark Brown <broonie@kernel.org>
Cc: nd <nd@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Szabolcs Nagy <szabolcs.nagy@arm.com>
Cc: Topi Miettinen <toiwoton@gmail.com>
Cc: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-02-02 22:33:24 -08:00
Alistair Popple
7d4a8be0c4 mm/mmu_notifier: remove unused mmu_notifier_range_update_to_read_only export 
mmu_notifier_range_update_to_read_only() was originally introduced in
commit c6d23413f8 ("mm/mmu_notifier:
mmu_notifier_range_update_to_read_only() helper") as an optimisation for
device drivers that know a range has only been mapped read-only.  However
there are no users of this feature so remove it.  As it is the only user
of the struct mmu_notifier_range.vma field remove that also.

Link: https://lkml.kernel.org/r/20230110025722.600912-1-apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-02-02 22:32:54 -08:00
Peter Xu
d1751118c8 mm/uffd: detect pgtable allocation failures 
Before this patch, when there's any pgtable allocation issues happened
during change_protection(), the error will be ignored from the syscall. 
For shmem, there will be an error dumped into the host dmesg.  Two issues
with that:

  (1) Doing a trace dump when allocation fails is not anything close to
      grace.

  (2) The user should be notified with any kind of such error, so the user
      can trap it and decide what to do next, either by retrying, or stop
      the process properly, or anything else.

For userfault users, this will change the API of UFFDIO_WRITEPROTECT when
pgtable allocation failure happened.  It should not normally break anyone,
though.  If it breaks, then in good ways.

One man-page update will be on the way to introduce the new -ENOMEM for
UFFDIO_WRITEPROTECT.  Not marking stable so we keep the old behavior on
the 5.19-till-now kernels.

[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/20230104225207.1066932-4-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: James Houghton <jthoughton@google.com>
Acked-by: James Houghton <jthoughton@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-01-18 17:12:53 -08:00