crypto: aesni - don't use GFP_ATOMIC allocation if the request doesn't cross a page in gcm

This patch fixes gcmaes_crypt_by_sg so that it won't use memory
allocation if the data doesn't cross a page boundary.

Authenticated encryption may be used by dm-crypt. If the encryption or
decryption fails, it would result in I/O error and filesystem corruption.
The function gcmaes_crypt_by_sg is using GFP_ATOMIC allocation that can
fail anytime. This patch fixes the logic so that it won't attempt the
failing allocation if the data doesn't cross a page boundary.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/x86/crypto/aesni-intel_glue.c

@@ -817,7 +817,7 @@ static int gcmaes_crypt_by_sg(bool enc, struct aead_request *req,
 	/* Linearize assoc, if not already linear */
 	if (req->src->length >= assoclen && req->src->length &&
 		(!PageHighMem(sg_page(req->src)) ||
-			req->src->offset + req->src->length < PAGE_SIZE)) {
+			req->src->offset + req->src->length <= PAGE_SIZE)) {
 		scatterwalk_start(&assoc_sg_walk, req->src);
 		assoc = scatterwalk_map(&assoc_sg_walk);
 	} else {