[PATCH v3] staging: rtl8723bs: stop overreading monitor interface name

[PATCH v3] staging: rtl8723bs: stop overreading monitor interface name

[Amirhossein Hajimohammadi]

From: AmirHossein HajiMohammadi <info@hajimohammadi.net>

cfg80211 passes a NUL-terminated interface name. memcpy() always reads
IFNAMSIZ + 1 bytes, even when the caller supplied a shorter string.

Use strscpy() to stop at the terminator and bound the write to the
destination buffer.

Signed-off-by: AmirHossein HajiMohammadi <info@hajimohammadi.net>
---
Changes in v3:
- Add an explicit From header matching the Signed-off-by identity.

Changes in v2:
- Send the patch inline instead of as a MIME attachment.

 drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c b/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
index 4416d0ec1..8f5032844 100644
--- a/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
+++ b/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
@@ -2158,7 +2158,7 @@ static int rtw_cfg80211_add_monitor_if(struct adapter *padapter, char *name, str
 		goto out;
 
 	*ndev = pwdev_priv->pmon_ndev = mon_ndev;
-	memcpy(pwdev_priv->ifname_mon, name, IFNAMSIZ + 1);
+	strscpy(pwdev_priv->ifname_mon, name);
 
 out:
 	if (ret && mon_wdev) {
-- 
2.39.5 (Apple Git-154)

Re: [PATCH v3] staging: rtl8723bs: stop overreading monitor interface name

[Greg KH]

On Tue, Sep 29, 2026 at 07:18:11PM +0330, Amirhossein Hajimohammadi wrote:
> From: AmirHossein HajiMohammadi <info@hajimohammadi.net>
> 
> cfg80211 passes a NUL-terminated interface name. memcpy() always reads
> IFNAMSIZ + 1 bytes, even when the caller supplied a shorter string.
> 
> Use strscpy() to stop at the terminator and bound the write to the
> destination buffer.
> 
> Signed-off-by: AmirHossein HajiMohammadi <info@hajimohammadi.net>
> ---
> Changes in v3:
> - Add an explicit From header matching the Signed-off-by identity.
> 
> Changes in v2:
> - Send the patch inline instead of as a MIME attachment.
> 
>  drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c b/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
> index 4416d0ec1..8f5032844 100644
> --- a/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
> +++ b/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
> @@ -2158,7 +2158,7 @@ static int rtw_cfg80211_add_monitor_if(struct adapter *padapter, char *name, str
>  		goto out;
>  
>  	*ndev = pwdev_priv->pmon_ndev = mon_ndev;
> -	memcpy(pwdev_priv->ifname_mon, name, IFNAMSIZ + 1);
> +	strscpy(pwdev_priv->ifname_mon, name);

But we are replacing str*() calls in the kernel with memcpy() calls
where it can happen, so why go backwards here?

What caused you to notice this change is needed?  Have you measured a
speed up in throughput with this change applied?  How was it tested?

thanks,

greg k-h

Re: [PATCH v3] staging: rtl8723bs: stop overreading monitor interface name

[Amirhossein Hajimohammadi]

You are right. I noticed this during manual source inspection and
incorrectly treated the fixed-size copy as something that should use a
string helper.

I did not measure any throughput improvement or test the change on
hardware. The original patch was only checked with checkpatch and by
applying the received email, so it is not sufficiently justified. Please
drop it.

On rechecking the code, ifname_mon is written and cleared but never read.
The appropriate cleanup is to remove the unused field and its dead stores
instead. I have compile-tested that cleanup with W=1 against staging-next
and will send it separately.

Sorry for the noise, and thanks for the review.