In the quest to remove all stack VLA usage from the kernel[1], this removes the discouraged use of AHASH_REQUEST_ON_STACK (and associated VLA) by switching to shash directly and keeping the associated descriptor allocated with the regular state on the heap. [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Acked-by: Arnd Bergmann <arnd@xxxxxxxx> --- drivers/net/ppp/ppp_mppe.c | 56 ++++++++++++++++++++------------------ 1 file changed, 30 insertions(+), 26 deletions(-) diff --git a/drivers/net/ppp/ppp_mppe.c b/drivers/net/ppp/ppp_mppe.c index 6c7fd98cb00a..a205750b431b 100644 --- a/drivers/net/ppp/ppp_mppe.c +++ b/drivers/net/ppp/ppp_mppe.c @@ -96,7 +96,7 @@ static inline void sha_pad_init(struct sha_pad *shapad) */ struct ppp_mppe_state { struct crypto_skcipher *arc4; - struct crypto_ahash *sha1; + struct shash_desc *sha1; unsigned char *sha1_digest; unsigned char master_key[MPPE_MAX_KEY_LEN]; unsigned char session_key[MPPE_MAX_KEY_LEN]; @@ -136,25 +136,16 @@ struct ppp_mppe_state { */ static void get_new_key_from_sha(struct ppp_mppe_state * state) { - AHASH_REQUEST_ON_STACK(req, state->sha1); - struct scatterlist sg[4]; - unsigned int nbytes; - - sg_init_table(sg, 4); - - nbytes = setup_sg(&sg[0], state->master_key, state->keylen); - nbytes += setup_sg(&sg[1], sha_pad->sha_pad1, - sizeof(sha_pad->sha_pad1)); - nbytes += setup_sg(&sg[2], state->session_key, state->keylen); - nbytes += setup_sg(&sg[3], sha_pad->sha_pad2, - sizeof(sha_pad->sha_pad2)); - - ahash_request_set_tfm(req, state->sha1); - ahash_request_set_callback(req, 0, NULL, NULL); - ahash_request_set_crypt(req, sg, state->sha1_digest, nbytes); - - crypto_ahash_digest(req); - ahash_request_zero(req); + crypto_shash_init(state->sha1); + crypto_shash_update(state->sha1, state->master_key, + state->keylen); + crypto_shash_update(state->sha1, sha_pad->sha_pad1, + sizeof(sha_pad->sha_pad1)); + crypto_shash_update(state->sha1, state->session_key, + state->keylen); + crypto_shash_update(state->sha1, sha_pad->sha_pad2, + sizeof(sha_pad->sha_pad2)); + crypto_shash_final(state->sha1, state->sha1_digest); } /* @@ -200,6 +191,7 @@ static void mppe_rekey(struct ppp_mppe_state * state, int initial_key) static void *mppe_alloc(unsigned char *options, int optlen) { struct ppp_mppe_state *state; + struct crypto_shash *shash; unsigned int digestsize; if (optlen != CILEN_MPPE + sizeof(state->master_key) || @@ -217,13 +209,21 @@ static void *mppe_alloc(unsigned char *options, int optlen) goto out_free; } - state->sha1 = crypto_alloc_ahash("sha1", 0, CRYPTO_ALG_ASYNC); - if (IS_ERR(state->sha1)) { - state->sha1 = NULL; + shash = crypto_alloc_shash("sha1", 0, 0); + if (IS_ERR(shash)) + goto out_free; + + state->sha1 = kmalloc(sizeof(*state->sha1) + + crypto_shash_descsize(shash), + GFP_KERNEL); + if (!state->sha1) { + crypto_free_shash(shash); goto out_free; } + state->sha1->tfm = shash; + state->sha1->flags = 0; - digestsize = crypto_ahash_digestsize(state->sha1); + digestsize = crypto_shash_digestsize(shash); if (digestsize < MPPE_MAX_KEY_LEN) goto out_free; @@ -246,7 +246,10 @@ static void *mppe_alloc(unsigned char *options, int optlen) out_free: kfree(state->sha1_digest); - crypto_free_ahash(state->sha1); + if (state->sha1) { + crypto_free_shash(state->sha1->tfm); + kzfree(state->sha1); + } crypto_free_skcipher(state->arc4); kfree(state); out: @@ -261,7 +264,8 @@ static void mppe_free(void *arg) struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg; if (state) { kfree(state->sha1_digest); - crypto_free_ahash(state->sha1); + crypto_free_shash(state->sha1->tfm); + kzfree(state->sha1); crypto_free_skcipher(state->arc4); kfree(state); } -- 2.17.1
