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crypto: hash - Remove VLA usage

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In the quest to remove all stack VLA usage from the kernel[1], this
removes the VLAs in SHASH_DESC_ON_STACK (via crypto_shash_descsize())
by using the maximum allowable size (which is now more clearly captured
in a macro), along with a few other cases. Similar limits are turned into
macros as well.

A review of existing sizes shows that SHA512_DIGEST_SIZE (64) is the
largest digest size and that sizeof(struct sha3_state) (360) is the
largest descriptor size. The corresponding maximums are reduced.

[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 14:18:38 -07:00 • committed by Herbert Xu
parent ebf533adc8
commit b68a7ec1e9
4 changed files with 11 additions and 7 deletions
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6
include/crypto/hash.h
View file

@ -151,9 +151,13 @@ struct shash_desc {
void *__ctx[] CRYPTO_MINALIGN_ATTR;
};
#define HASH_MAX_DIGESTSIZE 64
#define HASH_MAX_DESCSIZE 360
#define HASH_MAX_STATESIZE 512
#define SHASH_DESC_ON_STACK(shash, ctx) \
char __##shash##_desc[sizeof(struct shash_desc) + \
crypto_shash_descsize(ctx)] CRYPTO_MINALIGN_ATTR; \
HASH_MAX_DESCSIZE] CRYPTO_MINALIGN_ATTR; \
struct shash_desc *shash = (struct shash_desc *)__##shash##_desc
/**