From 6b3dcff7ca7e05c784ece15cc8d9c0bd913fbda4 Mon Sep 17 00:00:00 2001 From: Stephan Mueller Date: Thu, 18 Jan 2018 20:41:09 +0100 Subject: [PATCH] crypto: aesni - handle zero length dst buffer 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 Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman --- arch/x86/crypto/aesni-intel_glue.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/crypto/aesni-intel_glue.c b/arch/x86/crypto/aesni-intel_glue.c index 5c15d6b57329..fe2c7c16fd37 100644 --- a/arch/x86/crypto/aesni-intel_glue.c +++ b/arch/x86/crypto/aesni-intel_glue.c @@ -823,7 +823,7 @@ static int gcmaes_decrypt(struct aead_request *req, unsigned int assoclen, 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; -- 2.20.1