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crypto: shash - Remove VLA usage in unaligned hashing 

In the quest to remove all stack VLA usage from the kernel[1], this uses
the newly defined max alignment to perform unaligned hashing to avoid
VLAs, and drops the helper function while adding sanity checks on the
resulting buffer sizes. Additionally, the __aligned_largest macro is
removed since this helper was the only user.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Kees Cook 2018-08-07 14:18:42 -07:00 committed by Herbert Xu
parent 1299c9cfae
commit f3569fd613
2 changed files with 16 additions and 12 deletions
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27
crypto/shash.c
View File

@ -73,13 +73,6 @@ int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key,
}
EXPORT_SYMBOL_GPL(crypto_shash_setkey);
static inline unsigned int shash_align_buffer_size(unsigned len,
unsigned long mask)
{
typedef u8 __aligned_largest u8_aligned;
return len + (mask & ~(__alignof__(u8_aligned) - 1));
}
static int shash_update_unaligned(struct shash_desc *desc, const u8 *data,
unsigned int len)
{
@ -88,11 +81,17 @@ static int shash_update_unaligned(struct shash_desc *desc, const u8 *data,
unsigned long alignmask = crypto_shash_alignmask(tfm);
unsigned int unaligned_len = alignmask + 1 -
((unsigned long)data & alignmask);
u8 ubuf[shash_align_buffer_size(unaligned_len, alignmask)]
__aligned_largest;
/*
* We cannot count on __aligned() working for large values:
* https://patchwork.kernel.org/patch/9507697/
*/
u8 ubuf[MAX_ALGAPI_ALIGNMASK * 2];
u8 *buf = PTR_ALIGN(&ubuf[0], alignmask + 1);
int err;
if (WARN_ON(buf + unaligned_len > ubuf + sizeof(ubuf)))
return -EINVAL;
if (unaligned_len > len)
unaligned_len = len;
@ -124,11 +123,17 @@ static int shash_final_unaligned(struct shash_desc *desc, u8 *out)
unsigned long alignmask = crypto_shash_alignmask(tfm);
struct shash_alg *shash = crypto_shash_alg(tfm);
unsigned int ds = crypto_shash_digestsize(tfm);
u8 ubuf[shash_align_buffer_size(ds, alignmask)]
__aligned_largest;
/*
* We cannot count on __aligned() working for large values:
* https://patchwork.kernel.org/patch/9507697/
*/
u8 ubuf[MAX_ALGAPI_ALIGNMASK + HASH_MAX_DIGESTSIZE];
u8 *buf = PTR_ALIGN(&ubuf[0], alignmask + 1);
int err;
if (WARN_ON(buf + ds > ubuf + sizeof(ubuf)))
return -EINVAL;
err = shash->final(desc, buf);
if (err)
goto out;

1
include/linux/compiler_types.h
View File

@ -198,7 +198,6 @@ struct ftrace_likely_data {
*/
#define __pure __attribute__((pure))
#define __aligned(x) __attribute__((aligned(x)))
#define __aligned_largest __attribute__((aligned))
#define __printf(a, b) __attribute__((format(printf, a, b)))
#define __scanf(a, b) __attribute__((format(scanf, a, b)))
#define __maybe_unused __attribute__((unused))