linux-kernel - [PATCH][next] staging: rtl8188eu: Fix null pointer dereference on free

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Message-Id: <20210324152135.254152-1-colin.king@canonical.com>
Date:   Wed, 24 Mar 2021 15:21:35 +0000
From:   Colin King <colin.king@...onical.com>
To:     Larry Finger <Larry.Finger@...inger.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Martin Kaiser <martin@...ser.cx>, linux-staging@...ts.linux.dev
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] staging: rtl8188eu: Fix null pointer dereference on free_netdev call

From: Colin Ian King <colin.king@...onical.com>

An unregister_netdev call checks if pnetdev is null, hence a later
call to free_netdev can potentially be passing a null pointer, causing
a null pointer dereference. Avoid this by adding a null pointer check
on pnetdev before calling free_netdev.

Fixes: 1665c8fdffbb ("staging: rtl8188eu: use netdev routines for private data")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/staging/rtl8188eu/os_dep/usb_intf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8188eu/os_dep/usb_intf.c b/drivers/staging/rtl8188eu/os_dep/usb_intf.c
index 518e9feb3f46..91a3d34a1050 100644
--- a/drivers/staging/rtl8188eu/os_dep/usb_intf.c
+++ b/drivers/staging/rtl8188eu/os_dep/usb_intf.c
@@ -446,7 +446,8 @@ static void rtw_usb_if1_deinit(struct adapter *if1)
 	pr_debug("+r871xu_dev_remove, hw_init_completed=%d\n",
 		 if1->hw_init_completed);
 	rtw_free_drv_sw(if1);
-	free_netdev(pnetdev);
+	if (pnetdev)
+		free_netdev(pnetdev);
 }
 
 static int rtw_drv_init(struct usb_interface *pusb_intf, const struct usb_device_id *pdid)
-- 
2.30.2