linux-kernel - Re: [PATCH] net/9p/trans_virtio.c: add a terminal char for mount tag

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Message-ID: <5B616E3B.4050205@huawei.com>
Date:   Wed, 1 Aug 2018 16:24:27 +0800
From:   piaojun <piaojun@...wei.com>
To:     Dominique Martinet <asmadeus@...ewreck.org>
CC:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        <v9fs-developer@...ts.sourceforge.net>, Greg Kurz <groug@...d.org>
Subject: Re: [PATCH] net/9p/trans_virtio.c: add a terminal char for mount tag

Hi Dominique,

On 2018/8/1 16:11, Dominique Martinet wrote:
> piaojun wrote on Wed, Aug 01, 2018:
>> chan->tag has no terminal char at last which will result in printing messy
>> code when debugging code. So we should add '\0' for tag.
> 
> 9p is full of non null-terminated string so I'm not sure how I feel
> about it, is there anything wrong with how this is used or was this just
> when you tried to printf it?

There is nothing wrong at the places using tag, as they calculated the
tag_len carefully. Adding '\0' for it will make the code more robust. And
I'm glad to hear others' opinions.

Thanks,
Jun

> 
> If it's just for debugging I'd suggest using the printf format "%.*s"
> with "chan->tag_len, chan->tag" arguments,
> 
> 
> That said it's not like this is costly, so I'll take it if someone else
> thinks this is helpful
> 
>>
>> Signed-off-by: Jun Piao <piaojun@...wei.com>
>> ---
>>  net/9p/trans_virtio.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
>> index d422bfc..49d71d6 100644
>> --- a/net/9p/trans_virtio.c
>> +++ b/net/9p/trans_virtio.c
>> @@ -585,7 +585,7 @@ static int p9_virtio_probe(struct virtio_device *vdev)
>>  		err = -EINVAL;
>>  		goto out_free_vq;
>>  	}
>> -	tag = kmalloc(tag_len, GFP_KERNEL);
>> +	tag = kzalloc(tag_len + 1, GFP_KERNEL);
>>  	if (!tag) {
>>  		err = -ENOMEM;
>>  		goto out_free_vq;
>> --