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crypto: hash - Remove VLA usage 

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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4
crypto/ahash.c
View File

@ -550,8 +550,8 @@ static int ahash_prepare_alg(struct ahash_alg *alg)
{ {
struct crypto_alg *base = &alg->halg.base; struct crypto_alg *base = &alg->halg.base;
if (alg->halg.digestsize > PAGE_SIZE / 8 || if (alg->halg.digestsize > HASH_MAX_DIGESTSIZE ||
alg->halg.statesize > PAGE_SIZE / 8 || alg->halg.statesize > HASH_MAX_STATESIZE ||
alg->halg.statesize == 0) alg->halg.statesize == 0)
return -EINVAL; return -EINVAL;

2
crypto/algif_hash.c
View File

@ -239,7 +239,7 @@ static int hash_accept(struct socket *sock, struct socket *newsock, int flags,
struct alg_sock *ask = alg_sk(sk); struct alg_sock *ask = alg_sk(sk);
struct hash_ctx *ctx = ask->private; struct hash_ctx *ctx = ask->private;
struct ahash_request *req = &ctx->req; struct ahash_request *req = &ctx->req;
char state[crypto_ahash_statesize(crypto_ahash_reqtfm(req)) ? : 1]; char state[HASH_MAX_STATESIZE];
struct sock *sk2; struct sock *sk2;
struct alg_sock *ask2; struct alg_sock *ask2;
struct hash_ctx *ctx2; struct hash_ctx *ctx2;

6
crypto/shash.c
View File

@ -458,9 +458,9 @@ static int shash_prepare_alg(struct shash_alg *alg)
{ {
struct crypto_alg *base = &alg->base; struct crypto_alg *base = &alg->base;
if (alg->digestsize > PAGE_SIZE / 8 || if (alg->digestsize > HASH_MAX_DIGESTSIZE ||
alg->descsize > PAGE_SIZE / 8 || alg->descsize > HASH_MAX_DESCSIZE ||
alg->statesize > PAGE_SIZE / 8) alg->statesize > HASH_MAX_STATESIZE)
return -EINVAL; return -EINVAL;
base->cra_type = &crypto_shash_type; base->cra_type = &crypto_shash_type;

6
include/crypto/hash.h
View File

@ -151,9 +151,13 @@ struct shash_desc {
void *__ctx[] CRYPTO_MINALIGN_ATTR; 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) \ #define SHASH_DESC_ON_STACK(shash, ctx) \
char __##shash##_desc[sizeof(struct shash_desc) + \ 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 struct shash_desc *shash = (struct shash_desc *)__##shash##_desc
/** /**