[PATCH] mac80211: check skb_shared in ieee80211_8023_xmit()

From: Ryder Lee <ryder.lee@mediatek.com>
To: <linux-wireless@vger.kernel.org>
Cc: Felix Fietkau <nbd@nbd.name>,
	Lorenzo Bianconi <lorenzo.bianconi@redhat.com>,
	Shayne Chen <shayne.chen@mediatek.com>,
	"Evelyn Tsai" <evelyn.tsai@mediatek.com>,
	<linux-mediatek@lists.infradead.org>,
	"Ryder Lee" <ryder.lee@mediatek.com>
Subject: [PATCH] mac80211: check skb_shared in ieee80211_8023_xmit()
Date: Thu, 26 May 2022 17:08:53 +0800	[thread overview]
Message-ID: <1ef9b892cc93a36b1e62a6dda0e2e0a019f4e5f7.1653555361.git.ryder.lee@mediatek.com> (raw)

Add missing skb_shared check into 802.3 path as 802.11 path does
to prevent potential use-after-free from happening.

Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
---
 net/mac80211/tx.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 0e4efc08c762..b026e746ac5b 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -4437,7 +4437,7 @@ static void ieee80211_8023_xmit(struct ieee80211_sub_if_data *sdata,
 				struct net_device *dev, struct sta_info *sta,
 				struct ieee80211_key *key, struct sk_buff *skb)
 {
-	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct ieee80211_tx_info *info;
 	struct ieee80211_local *local = sdata->local;
 	struct tid_ampdu_tx *tid_tx;
 	u8 tid;
@@ -4452,6 +4452,17 @@ static void ieee80211_8023_xmit(struct ieee80211_sub_if_data *sdata,
 	    test_bit(SDATA_STATE_OFFCHANNEL, &sdata->state))
 		goto out_free;
 
+	if (skb_shared(skb)) {
+		struct sk_buff *tmp_skb = skb;
+
+		skb = skb_clone(skb, GFP_ATOMIC);
+		kfree_skb(tmp_skb);
+
+		if (!skb)
+			return;
+	}
+
+	info = IEEE80211_SKB_CB(skb);
 	memset(info, 0, sizeof(*info));
 
 	ieee80211_aggr_check(sdata, sta, skb);
-- 
2.29.2


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