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>
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@ -162,8 +162,10 @@ static int xor_tweak(struct skcipher_request *req, bool second_pass)
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}
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err = skcipher_walk_virt(&w, req, false);
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iv = (__be32 *)w.iv;
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if (err)
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return err;
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iv = (__be32 *)w.iv;
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counter[0] = be32_to_cpu(iv[3]);
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counter[1] = be32_to_cpu(iv[2]);
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counter[2] = be32_to_cpu(iv[1]);
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