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* [PATCH] staging: rtl8192e: fix potential use after free
@ 2019-11-05 14:49 Pan Bian
  2019-11-05 14:58 ` Dan Carpenter
  0 siblings, 1 reply; 2+ messages in thread
From: Pan Bian @ 2019-11-05 14:49 UTC (permalink / raw)
  To: Greg Kroah-Hartman, Himadri Pandya, YueHaibing, Colin Ian King
  Cc: devel, Pan Bian, linux-kernel

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>
---
 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 f932cb15e4e5..cdcb22f96ed9 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)
-- 
2.7.4

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^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] staging: rtl8192e: fix potential use after free
  2019-11-05 14:49 [PATCH] staging: rtl8192e: fix potential use after free Pan Bian
@ 2019-11-05 14:58 ` Dan Carpenter
  0 siblings, 0 replies; 2+ messages in thread
From: Dan Carpenter @ 2019-11-05 14:58 UTC (permalink / raw)
  To: Pan Bian
  Cc: devel, Greg Kroah-Hartman, YueHaibing, linux-kernel, Colin Ian King

On Tue, Nov 05, 2019 at 10:49:11PM +0800, Pan Bian wrote:
> 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>

regards,
dan carpenter

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devel mailing list
devel@linuxdriverproject.org
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

^ permalink raw reply	[flat|nested] 2+ messages in thread

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