[PATCH 3.16 079/366] crypto: ahash - Fix early termination in hash walk

[Ben Hutchings]

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

commit 900a081f6912a8985dc15380ec912752cb66025a upstream.

When we have an unaligned SG list entry where there is no leftover
aligned data, the hash walk code will incorrectly return zero as if
the entire SG list has been processed.

This patch fixes it by moving onto the next page instead.

Reported-by: Eli Cooper <elicooper@xxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 crypto/ahash.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/crypto/ahash.c
+++ b/crypto/ahash.c
@@ -90,13 +90,14 @@ int crypto_hash_walk_done(struct crypto_
 
 	if (nbytes && walk->offset & alignmask && !err) {
 		walk->offset = ALIGN(walk->offset, alignmask + 1);
-		walk->data += walk->offset;
-
 		nbytes = min(nbytes,
 			     ((unsigned int)(PAGE_SIZE)) - walk->offset);
 		walk->entrylen -= nbytes;
 
-		return nbytes;
+		if (nbytes) {
+			walk->data += walk->offset;
+			return nbytes;
+		}
 	}
 
 	if (walk->flags & CRYPTO_ALG_ASYNC)