From aec286cd36eacfd797e3d5dab8d5d23c15d1bb5e Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Tue, 9 Apr 2019 23:46:29 -0700 Subject: 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: # v4.20+ Cc: Ondrej Mosnacek Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu --- crypto/lrw.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'crypto') diff --git a/crypto/lrw.c b/crypto/lrw.c index 0430ccd08728..b6666c595a68 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]); -- cgit v1.2.3-59-g8ed1b