Re: [V9fs-developer] [PATCH] net/9p: Modify the problem of BUG_ON judgment

On 2018/8/3 12:23, Dominique Martinet wrote:

jiangyiwen wrote on Fri, Aug 03, 2018:

quoted

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.

Signed-off-by: Yiwen Jiang <redacted>

I'm not sure you've acted on his mail or if you found this
independantly, but this was reported by Dan Carpenter on the list in
June.
Would you mind if I add a tag for him?
Reported-by: Dan Carpenter <redacted> 

That aside this looks good, I'll take it.

Sorry, I didn't see it before, I tested this problem a few days ago.
It is true that this problem was discovered first by him. Thank you
for adding him.

quoted

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

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 6265d1d..08264ba 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c

@@ -191,7 +191,7 @@ static int pack_sg_list(struct scatterlist *sg, int start,
 		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);

@@ -236,6 +236,7 @@ static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
 		s = PAGE_SIZE - data_off;
 		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);