linux-kernel - Re: [PATCH linux-next] staging: ks7010: use strscpy() to instead of strncpy()

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Date:   Thu, 29 Dec 2022 12:45:10 +0300
From:   Dan Carpenter <error27@...il.com>
To:     yang.yang29@....com.cn
Cc:     gustavoars@...nel.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org, xu.panda@....com.cn
Subject: Re: [PATCH linux-next] staging: ks7010: use strscpy() to instead of
 strncpy()

On Mon, Dec 26, 2022 at 07:03:24PM +0800, yang.yang29@....com.cn wrote:
> From: Xu Panda <xu.panda@....com.cn>
> 
> The implementation of strscpy() is more robust and safer.
> That's now the recommended way to copy NUL-terminated strings.
> 
> Signed-off-by: Xu Panda <xu.panda@....com.cn>
> Signed-off-by: Yang Yang <yang.yang29@....com>
> ---
>  drivers/staging/ks7010/ks_wlan_net.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/ks7010/ks_wlan_net.c b/drivers/staging/ks7010/ks_wlan_net.c
> index 044c807ca022..e03c87f0bfe7 100644
> --- a/drivers/staging/ks7010/ks_wlan_net.c
> +++ b/drivers/staging/ks7010/ks_wlan_net.c
> @@ -382,8 +382,7 @@ static int ks_wlan_get_nick(struct net_device *dev,
>  		return -EPERM;
> 
>  	/* for SLEEP MODE */
> -	strncpy(extra, priv->nick, 16);
> -	extra[16] = '\0';
> +	strscpy(extra, priv->nick, 17);

I think this code is a buffer overflow.  This is an implementation of
SIOCGIWNICKN.

net/wireless/wext-core.c
   169          [IW_IOCTL_IDX(SIOCGIWNICKN)] = {
   170                  .header_type    = IW_HEADER_TYPE_POINT,
   171                  .token_size     = 1,
   172                  .max_tokens     = IW_ESSID_MAX_SIZE,
   173          },

As you can see there is a .max_tokens but no .min_tokens.  It is called
from ioctl_standard_iw_point().  So if the user specifies something
smaller than 17 it leads to a buffer overflow.

Your patch is mechanically correct, but now that we have eyes on the
code we should fix the security bug instead making checkpatch happy or
whatever.

regards,
dan carpenter