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Subject[PATCH 4.9 57/87] crypto: ccm - preserve the IV buffer
4.9-stable review patch.  If anyone has any objections, please let me know.


From: Romain Izard <>

commit 441f99c90497e15aa3ad1dbabd56187e29614348 upstream.

The IV buffer used during CCM operations is used twice, during both the
hashing step and the ciphering step.

When using a hardware accelerator that updates the contents of the IV
buffer at the end of ciphering operations, the value will be modified.
In the decryption case, the subsequent setup of the hashing algorithm
will interpret the updated IV instead of the original value, which can
lead to out-of-bounds writes.

Reuse the idata buffer, only used in the hashing step, to preserve the
IV's value during the ciphering step in the decryption case.

Signed-off-by: Romain Izard <>
Reviewed-by: Tudor Ambarus <>
Signed-off-by: Herbert Xu <>
Signed-off-by: Greg Kroah-Hartman <>

crypto/ccm.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/crypto/ccm.c
+++ b/crypto/ccm.c
@@ -413,7 +413,7 @@ static int crypto_ccm_decrypt(struct aea
unsigned int cryptlen = req->cryptlen;
u8 *authtag = pctx->auth_tag;
u8 *odata = pctx->odata;
- u8 *iv = req->iv;
+ u8 *iv = pctx->idata;
int err;

cryptlen -= authsize;
@@ -429,6 +429,8 @@ static int crypto_ccm_decrypt(struct aea
if (req->src != req->dst)
dst = pctx->dst;

+ memcpy(iv, req->iv, 16);
skcipher_request_set_tfm(skreq, ctx->ctr);
skcipher_request_set_callback(skreq, pctx->flags,
crypto_ccm_decrypt_done, req);

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