This is a note to let you know that I've just added the patch titled

crypto: skcipher - set walk.iv for zero-length inputs

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: crypto-skcipher-set-walk.iv-for-zero-length-inputs.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 2b4f27c36bcd46e820ddb9a8e6fe6a63fa4250b8 Mon Sep 17 00:00:00 2001

From: Eric Biggers ebiggers@google.com Date: Wed, 29 Nov 2017 01:18:57 -0800 Subject: crypto: skcipher - set walk.iv for zero-length inputs

From: Eric Biggers ebiggers@google.com

commit 2b4f27c36bcd46e820ddb9a8e6fe6a63fa4250b8 upstream.

All the ChaCha20 algorithms as well as the ARM bit-sliced AES-XTS algorithms call skcipher_walk_virt(), then access the IV (walk.iv) before checking whether any bytes need to be processed (walk.nbytes).

But if the input is empty, then skcipher_walk_virt() doesn't set the IV, and the algorithms crash trying to use the uninitialized IV pointer.

Fix it by setting the IV earlier in skcipher_walk_virt(). Also fix it for the AEAD walk functions.

This isn't a perfect solution because we can't actually align the IV to ->cra_alignmask unless there are bytes to process, for one because the temporary buffer for the aligned IV is freed by skcipher_walk_done(), which is only called when there are bytes to process. Thus, algorithms that require aligned IVs will still need to avoid accessing the IV when walk.nbytes == 0. Still, many algorithms/architectures are fine with IVs having any alignment, and even for those that aren't, a misaligned pointer bug is much less severe than an uninitialized pointer bug.

This change also matches the behavior of the older blkcipher_walk API.

Fixes: 0cabf2af6f5a ("crypto: skcipher - Fix crash on zero-length input") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- crypto/skcipher.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)

--- a/crypto/skcipher.c +++ b/crypto/skcipher.c @@ -449,6 +449,8 @@ static int skcipher_walk_skcipher(struct

walk->total = req->cryptlen; walk->nbytes = 0; + walk->iv = req->iv; + walk->oiv = req->iv;

if (unlikely(!walk->total)) return 0; @@ -456,9 +458,6 @@ static int skcipher_walk_skcipher(struct scatterwalk_start(&walk->in, req->src); scatterwalk_start(&walk->out, req->dst);

- walk->iv = req->iv; - walk->oiv = req->iv; - walk->flags &= ~SKCIPHER_WALK_SLEEP; walk->flags |= req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP ? SKCIPHER_WALK_SLEEP : 0; @@ -510,6 +509,8 @@ static int skcipher_walk_aead_common(str int err;

walk->nbytes = 0; + walk->iv = req->iv; + walk->oiv = req->iv;

if (unlikely(!walk->total)) return 0; @@ -525,9 +526,6 @@ static int skcipher_walk_aead_common(str scatterwalk_done(&walk->in, 0, walk->total); scatterwalk_done(&walk->out, 0, walk->total);

- walk->iv = req->iv; - walk->oiv = req->iv; - if (req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP) walk->flags |= SKCIPHER_WALK_SLEEP; else

Patches currently in stable-queue which might be from ebiggers@google.com are

queue-4.14/crypto-skcipher-set-walk.iv-for-zero-length-inputs.patch