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Subject[PATCH 5.0 047/238] crypto: x86/aesni-gcm - fix crash on empty plaintext
Date
5.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@google.com>

commit 3af349639597fea582a93604734d717e59a0e223 upstream.

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>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/crypto/aesni-intel_glue.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

--- a/arch/x86/crypto/aesni-intel_glue.c
+++ b/arch/x86/crypto/aesni-intel_glue.c
@@ -821,11 +821,14 @@ static int gcmaes_crypt_by_sg(bool enc,
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();

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