This is a note to let you know that I've just added the patch titled

crypto: aesni - handle zero length dst buffer

to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: crypto-aesni-handle-zero-length-dst-buffer.patch and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 9c674e1e2f9e24fa4392167efe343749008338e0 Mon Sep 17 00:00:00 2001

From: Stephan Mueller smueller@chronox.de Date: Thu, 18 Jan 2018 20:41:09 +0100 Subject: crypto: aesni - handle zero length dst buffer

From: Stephan Mueller smueller@chronox.de

commit 9c674e1e2f9e24fa4392167efe343749008338e0 upstream.

GCM can be invoked with a zero destination buffer. This is possible if the AAD and the ciphertext have zero lengths and only the tag exists in the source buffer (i.e. a source buffer cannot be zero). In this case, the GCM cipher only performs the authentication and no decryption operation.

When the destination buffer has zero length, it is possible that no page is mapped to the SG pointing to the destination. In this case, sg_page(req->dst) is an invalid access. Therefore, page accesses should only be allowed if the req->dst->length is non-zero which is the indicator that a page must exist.

This fixes a crash that can be triggered by user space via AF_ALG.

Signed-off-by: Stephan Mueller smueller@chronox.de 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 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/crypto/aesni-intel_glue.c +++ b/arch/x86/crypto/aesni-intel_glue.c @@ -824,7 +824,7 @@ static int gcmaes_decrypt(struct aead_re if (sg_is_last(req->src) && (!PageHighMem(sg_page(req->src)) || req->src->offset + req->src->length <= PAGE_SIZE) && - sg_is_last(req->dst) && + sg_is_last(req->dst) && req->dst->length && (!PageHighMem(sg_page(req->dst)) || req->dst->offset + req->dst->length <= PAGE_SIZE)) { one_entry_in_sg = 1;

Patches currently in stable-queue which might be from smueller@chronox.de are

queue-4.15/crypto-af_alg-whitelist-mask-and-type.patch queue-4.15/crypto-aesni-handle-zero-length-dst-buffer.patch