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coredump: Only sort VMAs when core_sort_vma sysctl is set

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The sorting of VMAs by size in commit 7d442a33bf ("binfmt_elf: Dump
smaller VMAs first in ELF cores") breaks elfutils[1]. Instead, sort
based on the setting of the new sysctl, core_sort_vma, which defaults
to 0, no sorting.

Reported-by: Michael Stapelberg <michael@stapelberg.ch>
Closes: https://lore.kernel.org/all/20250218085407.61126-1-michael@stapelberg.de/ [1]
Fixes: 7d442a33bf ("binfmt_elf: Dump smaller VMAs first in ELF cores")
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Kees Cook 2025-02-19 11:53:16 -08:00
parent a64dcfb451
commit 39ec9eaaa1
2 changed files with 24 additions and 2 deletions
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11
Documentation/admin-guide/sysctl/kernel.rst
View file

@ -212,6 +212,17 @@ pid>/``).
This value defaults to 0. This value defaults to 0.
core_sort_vma
=============
The default coredump writes VMAs in address order. By setting
``core_sort_vma`` to 1, VMAs will be written from smallest size
to largest size. This is known to break at least elfutils, but
can be handy when dealing with very large (and truncated)
coredumps where the more useful debugging details are included
in the smaller VMAs.
core_uses_pid core_uses_pid
============= =============

11
fs/coredump.c
View file

@ -63,6 +63,7 @@ static void free_vma_snapshot(struct coredump_params *cprm);
static int core_uses_pid; static int core_uses_pid;
static unsigned int core_pipe_limit; static unsigned int core_pipe_limit;
static unsigned int core_sort_vma;
static char core_pattern[CORENAME_MAX_SIZE] = "core"; static char core_pattern[CORENAME_MAX_SIZE] = "core";
static int core_name_size = CORENAME_MAX_SIZE; static int core_name_size = CORENAME_MAX_SIZE;
unsigned int core_file_note_size_limit = CORE_FILE_NOTE_SIZE_DEFAULT; unsigned int core_file_note_size_limit = CORE_FILE_NOTE_SIZE_DEFAULT;
@ -1026,6 +1027,15 @@ static const struct ctl_table coredump_sysctls[] = {
.extra1 = (unsigned int *)&core_file_note_size_min, .extra1 = (unsigned int *)&core_file_note_size_min,
.extra2 = (unsigned int *)&core_file_note_size_max, .extra2 = (unsigned int *)&core_file_note_size_max,
}, },
{
.procname = "core_sort_vma",
.data = &core_sort_vma,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_douintvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
}; };
static int __init init_fs_coredump_sysctls(void) static int __init init_fs_coredump_sysctls(void)
@ -1256,6 +1266,7 @@ static bool dump_vma_snapshot(struct coredump_params *cprm)
cprm->vma_data_size += m->dump_size; cprm->vma_data_size += m->dump_size;
} }
if (core_sort_vma)
sort(cprm->vma_meta, cprm->vma_count, sizeof(*cprm->vma_meta), sort(cprm->vma_meta, cprm->vma_count, sizeof(*cprm->vma_meta),
cmp_vma_size, NULL); cmp_vma_size, NULL);