2019-11-05 14:50:41

by Pan Bian

Subject: [PATCH] staging: rtl8192e: fix potential use after free

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 <[email protected]>
---
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

2019-11-05 16:58:09

by Dan Carpenter

Subject: Re: [PATCH] staging: rtl8192e: fix potential use after free

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 <[email protected]>

Reviewed-by: Dan Carpenter <[email protected]>

regards,
dan carpenter