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crypto: lrw - don't access already-freed walk.iv

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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: c778f96bf3 ("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>
This commit is contained in:
Eric Biggers 2019-04-09 23:46:29 -07:00 committed by Herbert Xu
parent 11fe71f146
commit aec286cd36
1 changed files with 3 additions and 1 deletions
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4
crypto/lrw.c
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@ -162,8 +162,10 @@ static int xor_tweak(struct skcipher_request *req, bool second_pass)
} }
err = skcipher_walk_virt(&w, req, false); err = skcipher_walk_virt(&w, req, false);
iv = (__be32 *)w.iv; if (err)
return err;
iv = (__be32 *)w.iv;
counter[0] = be32_to_cpu(iv[3]); counter[0] = be32_to_cpu(iv[3]);
counter[1] = be32_to_cpu(iv[2]); counter[1] = be32_to_cpu(iv[2]);
counter[2] = be32_to_cpu(iv[1]); counter[2] = be32_to_cpu(iv[1]);