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Date:   Fri, 3 Aug 2018 06:23:08 +0200
From:   Dominique Martinet <asmadeus@codewreck.org>
To:     jiangyiwen <jiangyiwen@huawei.com>
Cc:     Eric Van Hensbergen <ericvh@gmail.com>,
        Ron Minnich <rminnich@sandia.gov>,
        Latchesar Ionkov <lucho@ionkov.net>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        v9fs-developer@lists.sourceforge.net, netdev@vger.kernel.org
Subject: Re: [V9fs-developer] [PATCH] net/9p: Modify the problem of BUG_ON
 judgment
Message-ID: <20180803042308.GA4618@nautica>
References: <5B63D5F6.6080109@huawei.com>
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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@huawei.com>

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@oracle.com> 

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