[PATCH 2/3] [v2] staging: rtl8723bs: convert strncpy to strscpy

[Arnd Bergmann <arnd@kernel.org>]

From: Arnd Bergmann <arnd@arndb.de>

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>
---
v2:
  use the two-argument version of strscpy(), which is simpler for the constant
  size destination. Add the third instance in this driver as well.
---
 drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c | 5 ++---
 drivers/staging/rtl8723bs/os_dep/os_intfs.c       | 2 +-
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c b/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
index 65a450fcdce7..3fe27ee75b47 100644
--- a/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
+++ b/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;
 
diff --git a/drivers/staging/rtl8723bs/os_dep/os_intfs.c b/drivers/staging/rtl8723bs/os_dep/os_intfs.c
index 68bba3c0e757..55d0140cd543 100644
--- a/drivers/staging/rtl8723bs/os_dep/os_intfs.c
+++ b/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;
 }
-- 
2.39.2