From: Eric Biggers <ebiggers@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx> # v4.20+
Cc: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
crypto/lrw.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/crypto/lrw.c b/crypto/lrw.c
index 0430ccd087286..b6666c595a686 100644
--- a/crypto/lrw.c
+++ b/crypto/lrw.c
@@ -162,8 +162,10 @@ static int xor_tweak(struct skcipher_request *req, bool second_pass)
}
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[1] = be32_to_cpu(iv[2]);
counter[2] = be32_to_cpu(iv[1]);
--
2.21.0
