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

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Message-ID: <1491850565.4199.19.camel@sandisk.com>
Date:   Mon, 10 Apr 2017 18:56:06 +0000
From:   Bart Van Assche <Bart.VanAssche@...disk.com>
To:     "mb@...htnvm.io" <mb@...htnvm.io>,
        "jg@...htnvm.io" <jg@...htnvm.io>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "javier@...xlabs.com" <javier@...xlabs.com>
Subject: Re: [PATCH 1/3] lightnvm: convert sprintf into snprintf

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?

Bart.