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

[Dominique Martinet]

jiangyiwen wrote on Fri, Aug 03, 2018:
> 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 <jiangyiwen@xxxxxxxxxx>

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 <dan.carpenter@xxxxxxxxxx> 

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

> ---
>  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);

-- 
Dominique Martinet