From b7aa39a2ed0112d07fc277ebd24a08a7b2368ab9 Mon Sep 17 00:00:00 2001
From: Pan Bian <bianpan2016@163.com>
Date: Tue, 5 Nov 2019 22:49:11 +0800
Subject: [PATCH] staging: rtl8192e: fix potential use after free
Git-commit: b7aa39a2ed0112d07fc277ebd24a08a7b2368ab9
Patch-mainline: v5.5-rc1
References: bsc#1051510

The variable skb is released via kfree_skb() when the return value of
_rtl92e_tx is not zero. However, after that, skb is accessed again to
read its length, which may result in a use after free bug. This patch
fixes the bug by moving the release operation to where skb is never
used later.

Signed-off-by: Pan Bian <bianpan2016@163.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/1572965351-6745-1-git-send-email-bianpan2016@163.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/staging/rtl8192e/rtl8192e/rtl_core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/rtl8192e/rtl8192e/rtl_core.c b/drivers/staging/rtl8192e/rtl8192e/rtl_core.c
index b08712a9c029..dace81a7d1ba 100644
--- a/drivers/staging/rtl8192e/rtl8192e/rtl_core.c
+++ b/drivers/staging/rtl8192e/rtl8192e/rtl_core.c
@@ -1616,14 +1616,15 @@ static void _rtl92e_hard_data_xmit(struct sk_buff *skb, struct net_device *dev,
 	memcpy((unsigned char *)(skb->cb), &dev, sizeof(dev));
 	skb_push(skb, priv->rtllib->tx_headroom);
 	ret = _rtl92e_tx(dev, skb);
-	if (ret != 0)
-		kfree_skb(skb);
 
 	if (queue_index != MGNT_QUEUE) {
 		priv->rtllib->stats.tx_bytes += (skb->len -
 						 priv->rtllib->tx_headroom);
 		priv->rtllib->stats.tx_packets++;
 	}
+
+	if (ret != 0)
+		kfree_skb(skb);
 }
 
 static int _rtl92e_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
-- 
2.16.4