[PATCH AUTOSEL 5.3 018/292] staging: rtl8188eu: fix possible null dereference

[Sasha Levin <sashal@kernel.org>]

From: Connor Kuehl <connor.kuehl@canonical.com>

[ Upstream commit 228241944a48113470d3c3b46c88ba7fbe0a274b ]

Inside a nested 'else' block at the beginning of this function is a
call that assigns 'psta' to the return value of 'rtw_get_stainfo()'.
If 'rtw_get_stainfo()' returns NULL and the flow of control reaches
the 'else if' where 'psta' is dereferenced, then we will dereference
a NULL pointer.

Fix this by checking if 'psta' is not NULL before reading its
'psta->qos_option' data member.

Addresses-Coverity: ("Dereference null return value")

Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Link: https://lore.kernel.org/r/20190926150317.5894-1-connor.kuehl@canonical.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/staging/rtl8188eu/core/rtw_xmit.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/rtl8188eu/core/rtw_xmit.c b/drivers/staging/rtl8188eu/core/rtw_xmit.c
index 952f2ab513478..c37591657bac4 100644
--- a/drivers/staging/rtl8188eu/core/rtw_xmit.c
+++ b/drivers/staging/rtl8188eu/core/rtw_xmit.c
@@ -776,7 +776,7 @@ s32 rtw_make_wlanhdr(struct adapter *padapter, u8 *hdr, struct pkt_attrib *pattr
 			memcpy(pwlanhdr->addr2, get_bssid(pmlmepriv), ETH_ALEN);
 			memcpy(pwlanhdr->addr3, pattrib->src, ETH_ALEN);
 
-			if (psta->qos_option)
+			if (psta && psta->qos_option)
 				qos_option = true;
 		} else if (check_fwstate(pmlmepriv, WIFI_ADHOC_STATE) ||
 			   check_fwstate(pmlmepriv, WIFI_ADHOC_MASTER_STATE)) {
@@ -784,7 +784,7 @@ s32 rtw_make_wlanhdr(struct adapter *padapter, u8 *hdr, struct pkt_attrib *pattr
 			memcpy(pwlanhdr->addr2, pattrib->src, ETH_ALEN);
 			memcpy(pwlanhdr->addr3, get_bssid(pmlmepriv), ETH_ALEN);
 
-			if (psta->qos_option)
+			if (psta && psta->qos_option)
 				qos_option = true;
 		} else {
 			RT_TRACE(_module_rtl871x_xmit_c_, _drv_err_, ("fw_state:%x is not allowed to xmit frame\n", get_fwstate(pmlmepriv)));
-- 
2.20.1