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kexec_file: use SHA-256 library API instead of crypto_shash API

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This user of SHA-256 does not support any other algorithm, so the
crypto_shash abstraction provides no value.  Just use the SHA-256 library
API instead, which is much simpler and easier to use.

Tested with '/sbin/kexec --kexec-file-syscall'.

Link: https://lkml.kernel.org/r/20250428185721.844686-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Eric Biggers 2025-04-28 11:57:20 -07:00 • committed by Andrew Morton
parent c91d78622e
commit f7a667a046
2 changed files with 16 additions and 65 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
kernel/Kconfig.kexec
View file

@ -38,8 +38,7 @@ config KEXEC
config KEXEC_FILE
bool "Enable kexec file based system call"
depends on ARCH_SUPPORTS_KEXEC_FILE
select CRYPTO
select CRYPTO_SHA256
select CRYPTO_LIB_SHA256
select KEXEC_CORE
help
This is new version of kexec system call. This system call is

78
kernel/kexec_file.c
View file

@ -19,7 +19,6 @@
#include <linux/list.h>
#include <linux/fs.h>
#include <linux/ima.h>
#include <crypto/hash.h>
#include <crypto/sha2.h>
#include <linux/elf.h>
#include <linux/elfcore.h>
@ -712,11 +711,10 @@ int kexec_add_buffer(struct kexec_buf *kbuf)
/* Calculate and store the digest of segments */
static int kexec_calculate_store_digests(struct kimage *image)
{
struct crypto_shash *tfm;
struct shash_desc *desc;
struct sha256_state state;
int ret = 0, i, j, zero_buf_sz, sha_region_sz;
size_t desc_size, nullsz;
char *digest;
size_t nullsz;
u8 digest[SHA256_DIGEST_SIZE];
void *zero_buf;
struct kexec_sha_region *sha_regions;
struct purgatory_info *pi = &image->purgatory_info;
@ -727,37 +725,12 @@ static int kexec_calculate_store_digests(struct kimage *image)
zero_buf = __va(page_to_pfn(ZERO_PAGE(0)) << PAGE_SHIFT);
zero_buf_sz = PAGE_SIZE;
tfm = crypto_alloc_shash("sha256", 0, 0);
if (IS_ERR(tfm)) {
ret = PTR_ERR(tfm);
goto out;
}
desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
desc = kzalloc(desc_size, GFP_KERNEL);
if (!desc) {
ret = -ENOMEM;
goto out_free_tfm;
}
sha_region_sz = KEXEC_SEGMENT_MAX * sizeof(struct kexec_sha_region);
sha_regions = vzalloc(sha_region_sz);
if (!sha_regions) {
ret = -ENOMEM;
goto out_free_desc;
}
if (!sha_regions)
return -ENOMEM;
desc->tfm = tfm;
ret = crypto_shash_init(desc);
if (ret < 0)
goto out_free_sha_regions;
digest = kzalloc(SHA256_DIGEST_SIZE, GFP_KERNEL);
if (!digest) {
ret = -ENOMEM;
goto out_free_sha_regions;
}
sha256_init(&state);
for (j = i = 0; i < image->nr_segments; i++) {
struct kexec_segment *ksegment;
@ -776,10 +749,7 @@ static int kexec_calculate_store_digests(struct kimage *image)
if (ksegment->kbuf == pi->purgatory_buf)
continue;
ret = crypto_shash_update(desc, ksegment->kbuf,
ksegment->bufsz);
if (ret)
break;
sha256_update(&state, ksegment->kbuf, ksegment->bufsz);
/*
* Assume rest of the buffer is filled with zero and
@ -791,44 +761,26 @@ static int kexec_calculate_store_digests(struct kimage *image)
if (bytes > zero_buf_sz)
bytes = zero_buf_sz;
ret = crypto_shash_update(desc, zero_buf, bytes);
if (ret)
break;
sha256_update(&state, zero_buf, bytes);
nullsz -= bytes;
}
if (ret)
break;
sha_regions[j].start = ksegment->mem;
sha_regions[j].len = ksegment->memsz;
j++;
}
if (!ret) {
ret = crypto_shash_final(desc, digest);
if (ret)
goto out_free_digest;
ret = kexec_purgatory_get_set_symbol(image, "purgatory_sha_regions",
sha_regions, sha_region_sz, 0);
if (ret)
goto out_free_digest;
sha256_final(&state, digest);
ret = kexec_purgatory_get_set_symbol(image, "purgatory_sha256_digest",
digest, SHA256_DIGEST_SIZE, 0);
if (ret)
goto out_free_digest;
}
ret = kexec_purgatory_get_set_symbol(image, "purgatory_sha_regions",
sha_regions, sha_region_sz, 0);
if (ret)
goto out_free_sha_regions;
out_free_digest:
kfree(digest);
ret = kexec_purgatory_get_set_symbol(image, "purgatory_sha256_digest",
digest, SHA256_DIGEST_SIZE, 0);
out_free_sha_regions:
vfree(sha_regions);
out_free_desc:
kfree(desc);
out_free_tfm:
kfree(tfm);
out:
return ret;
}