linux-kernel - [PATCH 5.0 043/123] crypto: arm64/aes-neonbs

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Date:   Mon, 20 May 2019 14:13:43 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Biggers <ebiggers@...gle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 5.0 043/123] crypto: arm64/aes-neonbs - dont access already-freed walk.iv

From: Eric Biggers <ebiggers@...gle.com>

commit 4a8108b70508df0b6c4ffa4a3974dab93dcbe851 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.

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 unconditionally accessing walk.iv has caused a
real problem in other algorithms.  Thus, update xts-aes-neonbs to start
checking the return value of skcipher_walk_virt().

Fixes: 1abee99eafab ("crypto: arm64/aes - reimplement bit-sliced ARM/NEON implementation for arm64")
Cc: <stable@...r.kernel.org> # v4.11+
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm64/crypto/aes-neonbs-glue.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/arm64/crypto/aes-neonbs-glue.c
+++ b/arch/arm64/crypto/aes-neonbs-glue.c
@@ -304,6 +304,8 @@ static int __xts_crypt(struct skcipher_r
 	int err;

 	err = skcipher_walk_virt(&walk, req, false);
+	if (err)
+		return err;

 	kernel_neon_begin();
 	neon_aes_ecb_encrypt(walk.iv, walk.iv, ctx->twkey, ctx->key.rounds, 1);