linux-kernel - Re: [PATCH 1/3] lightnvm: convert sprintf into snprintf

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Date:   Tue, 11 Apr 2017 08:31:12 +0200
From:   Javier González <jg@...htnvm.io>
To:     Bart Van Assche <Bart.VanAssche@...disk.com>
Cc:     Matias Bjørling <mb@...htnvm.io>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Subject: Re: [PATCH 1/3] lightnvm: convert sprintf into snprintf

> On 10 Apr 2017, at 20.56, Bart Van Assche <Bart.VanAssche@...disk.com> wrote:
> 
> On Mon, 2017-04-10 at 20:51 +0200, Javier González wrote:
>> Convert sprintf calls to snprintf in order to make possible buffer
>> overflow more obvious.
>> 
>> Signed-off-by: Javier González <javier@...xlabs.com>
>> ---
>> drivers/lightnvm/core.c | 7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
>> index c3340ef..bdbb333 100644
>> --- a/drivers/lightnvm/core.c
>> +++ b/drivers/lightnvm/core.c
>> @@ -272,7 +272,8 @@ static int nvm_create_tgt(struct nvm_dev *dev, struct nvm_ioctl_create *create)
>> 		goto err_disk;
>> 	blk_queue_make_request(tqueue, tt->make_rq);
>> 
>> -	sprintf(tdisk->disk_name, "%s", create->tgtname);
>> +	snprintf(tdisk->disk_name, sizeof(tdisk->disk_name), "%s",
>> +							create->tgtname);
>> 	tdisk->flags = GENHD_FL_EXT_DEVT;
>> 	tdisk->major = 0;
>> 	tdisk->first_minor = 0;
>> @@ -1195,13 +1196,13 @@ static long nvm_ioctl_get_devices(struct file *file, void __user *arg)
>> 	list_for_each_entry(dev, &nvm_devices, devices) {
>> 		struct nvm_ioctl_device_info *info = &devices->info[i];
>> 
>> -		sprintf(info->devname, "%s", dev->name);
>> +		snprintf(info->devname, sizeof(info->devname), "%s", dev->name);
>> 
>> 		/* kept for compatibility */
>> 		info->bmversion[0] = 1;
>> 		info->bmversion[1] = 0;
>> 		info->bmversion[2] = 0;
>> -		sprintf(info->bmname, "%s", "gennvm");
>> +		snprintf(info->bmname, sizeof(info->bmname), "%s", "gennvm");
>> 		i++;
>> 
>> 		if (i > 31) {
> 
> Hello Javier,
> 
> Although the above changes look fine to me, have you considered to use strlcpy()
> instead of snprintf() for these string copy operations?

You're right. It is a better way of doing it.

Thanks!

> 
> Bart.

Javier

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