[PATCH 3.18 04/29] 9p/virtio: fix off-by-one error in sg list bounds check

[Greg Kroah-Hartman]

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

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

From: jiangyiwen <jiangyiwen@xxxxxxxxxx>

commit 23cba9cbde0bba05d772b335fe5f66aa82b9ad19 upstream.

Because the value of limit is VIRTQUEUE_NUM, if index is equal to
limit, it will cause sg array out of bounds, so correct the judgement
of BUG_ON.

Link: http://lkml.kernel.org/r/5B63D5F6.6080109@xxxxxxxxxx
Signed-off-by: Yiwen Jiang <jiangyiwen@xxxxxxxxxx>
Reported-By: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Acked-by: Jun Piao <piaojun@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Dominique Martinet <dominique.martinet@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 net/9p/trans_virtio.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -192,7 +192,7 @@ static int pack_sg_list(struct scatterli
 		s = rest_of_page(data);
 		if (s > count)
 			s = count;
-		BUG_ON(index > limit);
+		BUG_ON(index >= limit);
 		/* Make sure we don't terminate early. */
 		sg_unmark_end(&sg[index]);
 		sg_set_buf(&sg[index++], data, s);
@@ -238,6 +238,7 @@ pack_sg_list_p(struct scatterlist *sg, i
 		s = rest_of_page(data);
 		if (s > count)
 			s = count;
+		BUG_ON(index >= limit);
 		/* Make sure we don't terminate early. */
 		sg_unmark_end(&sg[index]);
 		sg_set_page(&sg[index++], pdata[i++], s, data_off);