staging: rtl8723bs: convert strncpy to strscpy

gcc-9 complains about a possibly unterminated string in the strncpy() destination:

In function 'rtw_cfg80211_add_monitor_if',
    inlined from 'cfg80211_rtw_add_virtual_intf' at drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c:2209:9:
drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c:2146:2: error: 'strncpy' specified bound 16 equals destination size [-Werror=stringop-truncation]
 2146 |  strncpy(mon_ndev->name, name, IFNAMSIZ);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This one is a false-positive because of the explicit termination in the following
line, and recent versions of clang and gcc no longer warn about this.

Interestingly, the other strncpy() in this file is missing a termination but
does not produce a warning, possibly because of the type confusion and the
cast between u8 and char.

Change both strncpy() instances to strscpy(), which avoids the warning as well
as the possibly missing termination. No additional padding is needed here.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://github.com/KSPP/linux/issues/90Reviewed-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/20240408194821.3183462-2-arnd@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c

@@ -884,7 +884,7 @@ static int cfg80211_rtw_add_key(struct wiphy *wiphy, struct net_device *ndev,
 		goto addkey_end;
 	}
 
-	strncpy((char *)param->u.crypt.alg, alg_name, IEEE_CRYPT_ALG_NAME_LEN);
+	strscpy(param->u.crypt.alg, alg_name);
 
 	if (!mac_addr || is_broadcast_ether_addr(mac_addr))
 		param->u.crypt.set_tx = 0; /* for wpa/wpa2 group key */
@@ -2143,8 +2143,7 @@ static int rtw_cfg80211_add_monitor_if(struct adapter *padapter, char *name, str
 	}
 
 	mon_ndev->type = ARPHRD_IEEE80211_RADIOTAP;
-	strncpy(mon_ndev->name, name, IFNAMSIZ);
-	mon_ndev->name[IFNAMSIZ - 1] = 0;
+	strscpy(mon_ndev->name, name);
 	mon_ndev->needs_free_netdev = true;
 	mon_ndev->priv_destructor = rtw_ndev_destructor;
 

drivers/staging/rtl8723bs/os_dep/os_intfs.c

@@ -415,7 +415,7 @@ static int rtw_ndev_init(struct net_device *dev)
 	struct adapter *adapter = rtw_netdev_priv(dev);
 
 	netdev_dbg(dev, FUNC_ADPT_FMT "\n", FUNC_ADPT_ARG(adapter));
-	strncpy(adapter->old_ifname, dev->name, IFNAMSIZ);
+	strscpy(adapter->old_ifname, dev->name);
 
 	return 0;
 }