[PATCH 4.19 269/321] staging: rtl8192e: fix potential use after free

Greg Kroah-Hartman
2019-12-03T22:56:48Z

From: Pan Bian <bianpan2016@163.com>

commit b7aa39a2ed0112d07fc277ebd24a08a7b2368ab9 upstream.

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>

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

--- a/drivers/staging/rtl8192e/rtl8192e/rtl_core.c
+++ b/drivers/staging/rtl8192e/rtl8192e/rtl_core.c
@@ -1627,14 +1627,15 @@ static void _rtl92e_hard_data_xmit(struc
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)