Commit b68a7ec1 authored by Kees Cook's avatar Kees Cook Committed by Herbert Xu
Browse files

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: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent ebf533ad

crypto/ahash.c

+2 −2
Original line number Diff line number Diff line
@@ -550,8 +550,8 @@ static int ahash_prepare_alg(struct ahash_alg *alg) 
{

	struct crypto_alg *base = &alg->halg.base;



	if (alg->halg.digestsize > PAGE_SIZE / 8 ||

	    alg->halg.statesize > PAGE_SIZE / 8 ||

	if (alg->halg.digestsize > HASH_MAX_DIGESTSIZE ||

	    alg->halg.statesize > HASH_MAX_STATESIZE ||

	    alg->halg.statesize == 0)

		return -EINVAL;

crypto/algif_hash.c

+1 −1
Original line number Diff line number Diff line
@@ -239,7 +239,7 @@ static int hash_accept(struct socket *sock, struct socket *newsock, int flags, 
	struct alg_sock *ask = alg_sk(sk);

	struct hash_ctx *ctx = ask->private;

	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 alg_sock *ask2;

	struct hash_ctx *ctx2;

crypto/shash.c

+3 −3
Original line number Diff line number Diff line
@@ -458,9 +458,9 @@ static int shash_prepare_alg(struct shash_alg *alg) 
{

	struct crypto_alg *base = &alg->base;



	if (alg->digestsize > PAGE_SIZE / 8 ||

	    alg->descsize > PAGE_SIZE / 8 ||

	    alg->statesize > PAGE_SIZE / 8)

	if (alg->digestsize > HASH_MAX_DIGESTSIZE ||

	    alg->descsize > HASH_MAX_DESCSIZE ||

	    alg->statesize > HASH_MAX_STATESIZE)

		return -EINVAL;



	base->cra_type = &crypto_shash_type;

include/crypto/hash.h

+5 −1
Original line number Diff line number Diff line
@@ -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



/**

CRA Git | Maintained and supported by SUSTech CRA and CCSE