[PATCH] gcmaes_crypt_by_sg: don't use GFP_ATOMIC allocation if the request doesn't cross a page

[Mikulas Patocka]

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 <mpato...@redhat.com>
Cc: sta...@vger.kernel.org

---
 arch/x86/crypto/aesni-intel_glue.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/arch/x86/crypto/aesni-intel_glue.c
===================================================================
--- linux-2.6.orig/arch/x86/crypto/aesni-intel_glue.c   2018-05-31 
18:04:37.808000000 +0200
+++ linux-2.6/arch/x86/crypto/aesni-intel_glue.c        2018-09-04 
21:56:35.330000000 +0200
@@ -817,7 +817,7 @@ static int gcmaes_crypt_by_sg(bool enc,
        /* 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 {