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ppp: mppe: Remove VLA usage

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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@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kees Cook 2018-08-03 09:37:45 -07:00 committed by David S. Miller
parent eb9950eb31
commit a394b3af20
1 changed files with 30 additions and 26 deletions
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56
drivers/net/ppp/ppp_mppe.c
View file

@ -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);
}