crypto: lrw - don't access already-freed walk.iv
authorEric Biggers <ebiggers@google.com>
Wed, 10 Apr 2019 06:46:29 +0000 (23:46 -0700)
committerHerbert Xu <herbert@gondor.apana.org.au>
Thu, 18 Apr 2019 14:14:58 +0000 (22:14 +0800)
commitaec286cd36eacfd797e3d5dab8d5d23c15d1bb5e
tree2fc6e16572eaea0884bbaaea1135f9bb1de302dd
parent11fe71f146ee652a30ffc3c204105c2d81a00d1c
crypto: lrw - don't access already-freed walk.iv

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.

Fix this in the LRW template by checking the return value of
skcipher_walk_virt().

This bug was detected by my patches that improve testmgr to fuzz
algorithms against their generic implementation.  When the extra
self-tests were run on a KASAN-enabled kernel, a KASAN use-after-free
splat occured during lrw(aes) testing.

Fixes: c778f96bf347 ("crypto: lrw - Optimize tweak computation")
Cc: <stable@vger.kernel.org> # v4.20+
Cc: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
crypto/lrw.c