linux-kernel - Re: [V9fs-developer] [PATCH] net/9p: Modify the problem of BUG

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Message-ID: <5B63F396.3090507@huawei.com>
Date:   Fri, 3 Aug 2018 14:17:58 +0800
From:   jiangyiwen <jiangyiwen@...wei.com>
To:     Dominique Martinet <asmadeus@...ewreck.org>
CC:     Eric Van Hensbergen <ericvh@...il.com>,
        Ron Minnich <rminnich@...dia.gov>,
        Latchesar Ionkov <lucho@...kov.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        <v9fs-developer@...ts.sourceforge.net>, <netdev@...r.kernel.org>
Subject: 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:
>> 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@...wei.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@...cle.com> 
> 
> 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.

>> ---
>>  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);
>