[PATCH 3.16 037/132] crypto: arm/aes-neonbs - don't access already-freed walk.iv

[Ben Hutchings]

3.16.74-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@xxxxxxxxxx>

commit 767f015ea0b7ab9d60432ff6cd06b664fd71f50f upstream.

If the user-provided IV needs to be aligned to the algorithm's
alignmask, then skcipher_walk_virt() copies the IV into a new aligned
buffer walk.iv.  But skcipher_walk_virt() can fail afterwards, and then
if the caller unconditionally accesses walk.iv, it's a use-after-free.

arm32 xts-aes-neonbs doesn't set an alignmask, so currently it isn't
affected by this despite unconditionally accessing walk.iv.  However
this is more subtle than desired, and it was actually broken prior to
the alignmask being removed by commit cc477bf64573 ("crypto: arm/aes -
replace bit-sliced OpenSSL NEON code").  Thus, update xts-aes-neonbs to
start checking the return value of skcipher_walk_virt().

Fixes: e4e7f10bfc40 ("ARM: add support for bit sliced AES using NEON instructions")
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/arm/crypto/aesbs-glue.c | 4 ++++
 1 file changed, 4 insertions(+)

--- a/arch/arm/crypto/aesbs-glue.c
+++ b/arch/arm/crypto/aesbs-glue.c
@@ -259,6 +259,8 @@ static int aesbs_xts_encrypt(struct blkc
 
 	blkcipher_walk_init(&walk, dst, src, nbytes);
 	err = blkcipher_walk_virt_block(desc, &walk, 8 * AES_BLOCK_SIZE);
+	if (err)
+		return err;
 
 	/* generate the initial tweak */
 	AES_encrypt(walk.iv, walk.iv, &ctx->twkey);
@@ -283,6 +285,8 @@ static int aesbs_xts_decrypt(struct blkc
 
 	blkcipher_walk_init(&walk, dst, src, nbytes);
 	err = blkcipher_walk_virt_block(desc, &walk, 8 * AES_BLOCK_SIZE);
+	if (err)
+		return err;
 
 	/* generate the initial tweak */
 	AES_encrypt(walk.iv, walk.iv, &ctx->twkey);