[PATCH 3.12 53/76] crypto: hash - Fix page length clamping in hash walk

[Jiri Slaby]

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 13f4bb78cf6a312bbdec367ba3da044b09bf0e29 upstream.

The crypto hash walk code is broken when supplied with an offset
greater than or equal to PAGE_SIZE.  This patch fixes it by adjusting
walk->pg and walk->offset when this happens.

Reported-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 crypto/ahash.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/crypto/ahash.c b/crypto/ahash.c
index b246858ca032..781a8a73a7ff 100644
--- a/crypto/ahash.c
+++ b/crypto/ahash.c
@@ -64,8 +64,9 @@ static int hash_walk_new_entry(struct crypto_hash_walk *walk)
 	struct scatterlist *sg;
 
 	sg = walk->sg;
-	walk->pg = sg_page(sg);
 	walk->offset = sg->offset;
+	walk->pg = sg_page(walk->sg) + (walk->offset >> PAGE_SHIFT);
+	walk->offset = offset_in_page(walk->offset);
 	walk->entrylen = sg->length;
 
 	if (walk->entrylen > walk->total)
-- 
2.8.2