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From:   Lv Yunlong <lyl2019@mail.ustc.edu.cn>
To:     j@w1.fi, kvalo@codeaurora.org, davem@davemloft.net, kuba@kernel.org
Cc:     linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Subject: [PATCH] wireless: hostap: Fix a use after free in hostap_80211_rx
Date:   Mon, 29 Mar 2021 04:00:21 -0700
Message-Id: <20210329110021.7497-1-lyl2019@mail.ustc.edu.cn>
MIME-Version: 1.0
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Function hostap_80211_rx() calls prism2_rx_80211(..,skb,..). In
prism2_rx_80211, i found that the skb could be freed by dev_kfree_skb_any(skb)
and return 0. Also could be freed by netif_rx(skb) when netif_rx return
NET_RX_DROP.

But after called the prism2_rx_80211(..,skb,..), the skb is used by skb->len.

As the new skb->len is returned by prism2_rx_80211(), my patch uses a variable
len to repalce skb->len. According to another useage of prism2_rx_80211 in
monitor_rx().

Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
---
 drivers/net/wireless/intersil/hostap/hostap_80211_rx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/intersil/hostap/hostap_80211_rx.c b/drivers/net/wireless/intersil/hostap/hostap_80211_rx.c
index 61be822f90b5..a45ee7b35533 100644
--- a/drivers/net/wireless/intersil/hostap/hostap_80211_rx.c
+++ b/drivers/net/wireless/intersil/hostap/hostap_80211_rx.c
@@ -1016,10 +1016,10 @@ void hostap_80211_rx(struct net_device *dev, struct sk_buff *skb,
 			if (local->hostapd && local->apdev) {
 				/* Send IEEE 802.1X frames to the user
 				 * space daemon for processing */
-				prism2_rx_80211(local->apdev, skb, rx_stats,
+				int len = prism2_rx_80211(local->apdev, skb, rx_stats,
 						PRISM2_RX_MGMT);
 				local->apdevstats.rx_packets++;
-				local->apdevstats.rx_bytes += skb->len;
+				local->apdevstats.rx_bytes += len;
 				goto rx_exit;
 			}
 		} else if (!frame_authorized) {
-- 
2.25.1