linux-kernel - [PATCH v2] staging: rtl8188eu: fix possible null dereference

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Message-Id: <20190926150317.5894-1-connor.kuehl@canonical.com>
Date:   Thu, 26 Sep 2019 08:03:17 -0700
From:   Connor Kuehl <connor.kuehl@...onical.com>
To:     Larry.Finger@...inger.net, gregkh@...uxfoundation.org,
        straube.linux@...il.com, devel@...verdev.osuosl.org
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH v2] staging: rtl8188eu: fix possible null dereference

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@...onical.com>
---
v1 -> v2:
  - Add the same null check to line 779

 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 952f2ab51347..c37591657bac 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)));
-- 
2.17.1