[PATCH 3.16 073/114] crypto: hash - Fix page length clamping in hash walk

[Ben Hutchings]

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

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

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

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: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 crypto/ahash.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/crypto/ahash.c
+++ b/crypto/ahash.c
@@ -68,8 +68,9 @@ static int hash_walk_new_entry(struct cr
 	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)