From: Eric Biggers ebiggers@google.com

gcmaes_crypt_by_sg() dereferences the NULL pointer returned by scatterwalk_ffwd() when encrypting an empty plaintext and the source scatterlist ends immediately after the associated data.

Fix it by only fast-forwarding to the src/dst data scatterlists if the data length is nonzero.

This bug is reproduced by the "rfc4543(gcm(aes))" test vectors when run with the new AEAD test manager.

Fixes: e845520707f8 ("crypto: aesni - Update aesni-intel_glue to use scatter/gather") Cc: stable@vger.kernel.org # v4.17+ Cc: Dave Watson davejwatson@fb.com Signed-off-by: Eric Biggers ebiggers@google.com --- arch/x86/crypto/aesni-intel_glue.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/x86/crypto/aesni-intel_glue.c b/arch/x86/crypto/aesni-intel_glue.c index 9b5ccde3ef31..1e3d2102033a 100644 --- a/arch/x86/crypto/aesni-intel_glue.c +++ b/arch/x86/crypto/aesni-intel_glue.c @@ -813,11 +813,14 @@ static int gcmaes_crypt_by_sg(bool enc, struct aead_request *req, scatterwalk_map_and_copy(assoc, req->src, 0, assoclen, 0); }

- src_sg = scatterwalk_ffwd(src_start, req->src, req->assoclen); - scatterwalk_start(&src_sg_walk, src_sg); - if (req->src != req->dst) { - dst_sg = scatterwalk_ffwd(dst_start, req->dst, req->assoclen); - scatterwalk_start(&dst_sg_walk, dst_sg); + if (left) { + src_sg = scatterwalk_ffwd(src_start, req->src, req->assoclen); + scatterwalk_start(&src_sg_walk, src_sg); + if (req->src != req->dst) { + dst_sg = scatterwalk_ffwd(dst_start, req->dst, + req->assoclen); + scatterwalk_start(&dst_sg_walk, dst_sg); + } }

kernel_fpu_begin();