[PATCH] Crypto : Fix Null deref in scatterwalk_pagedone

[Manas]

`sg_next` can return NULL which causes NULL deref in
`scatterwalk_start`

Reported-by: Manas Ghandat <ghandatmanas@xxxxxxxxx>
Reported-by: Rakshit Awasthi <rakshitawasthi17@xxxxxxxxx>
Signed-off-by: Manas Ghandat <ghandatmanas@xxxxxxxxx>
Signed-off-by: Rakshit Awasthi <rakshitawasthi17@xxxxxxxxx>
---
 include/crypto/scatterwalk.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/crypto/scatterwalk.h b/include/crypto/scatterwalk.h
index 32fc4473175b..abbb67391710 100644
--- a/include/crypto/scatterwalk.h
+++ b/include/crypto/scatterwalk.h
@@ -78,7 +78,8 @@ static inline void scatterwalk_pagedone(struct scatter_walk *walk, int out,
 		page = sg_page(walk->sg) + ((walk->offset - 1) >> PAGE_SHIFT);
 		flush_dcache_page(page);
 	}
-
+	if (sg_next(walk->sg) == NULL)
+		return;
 	if (more && walk->offset >= walk->sg->offset + walk->sg->length)
 		scatterwalk_start(walk, sg_next(walk->sg));
 }
-- 
2.43.0