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Date:   Tue, 19 Jul 2022 21:16:01 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ryder Lee <ryder.lee@...iatek.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Sasha Levin <sashal@...nel.org>, johannes@...solutions.net,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, matthias.bgg@...il.com,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.10 10/25] wifi: mac80211: check skb_shared in ieee80211_8023_xmit()

From: Ryder Lee <ryder.lee@...iatek.com>

[ Upstream commit a4926abb787e2ef3ee2997e6ca8844d859478647 ]

Add a missing skb_shared check into 802.3 path to prevent potential
use-after-free from happening. This also uses skb_share_check()
instead of open-coding in tx path.

Signed-off-by: Ryder Lee <ryder.lee@...iatek.com>
Link: https://lore.kernel.org/r/e7a73aaf7742b17e43421c56625646dfc5c4d2cb.1653571902.git.ryder.lee@mediatek.com
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/mac80211/tx.c | 36 +++++++++++++-----------------------
 1 file changed, 13 insertions(+), 23 deletions(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index bbbcc678c655..36e1eb9b2fff 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2811,19 +2811,10 @@ static struct sk_buff *ieee80211_build_hdr(struct ieee80211_sub_if_data *sdata,
 	/*
 	 * If the skb is shared we need to obtain our own copy.
 	 */
-	if (skb_shared(skb)) {
-		struct sk_buff *tmp_skb = skb;
-
-		/* can't happen -- skb is a clone if info_id != 0 */
-		WARN_ON(info_id);
-
-		skb = skb_clone(skb, GFP_ATOMIC);
-		kfree_skb(tmp_skb);
-
-		if (!skb) {
-			ret = -ENOMEM;
-			goto free;
-		}
+	skb = skb_share_check(skb, GFP_ATOMIC);
+	if (unlikely(!skb)) {
+		ret = -ENOMEM;
+		goto free;
 	}
 
 	hdr.frame_control = fc;
@@ -3526,15 +3517,9 @@ static bool ieee80211_xmit_fast(struct ieee80211_sub_if_data *sdata,
 
 	/* after this point (skb is modified) we cannot return false */
 
-	if (skb_shared(skb)) {
-		struct sk_buff *tmp_skb = skb;
-
-		skb = skb_clone(skb, GFP_ATOMIC);
-		kfree_skb(tmp_skb);
-
-		if (!skb)
-			return true;
-	}
+	skb = skb_share_check(skb, GFP_ATOMIC);
+	if (unlikely(!skb))
+		return true;
 
 	if ((hdr->frame_control & cpu_to_le16(IEEE80211_STYPE_QOS_DATA)) &&
 	    ieee80211_amsdu_aggregate(sdata, sta, fast_tx, skb))
@@ -4244,7 +4229,7 @@ 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;
@@ -4259,6 +4244,11 @@ static void ieee80211_8023_xmit(struct ieee80211_sub_if_data *sdata,
 	    test_bit(SDATA_STATE_OFFCHANNEL, &sdata->state))
 		goto out_free;
 
+	skb = skb_share_check(skb, GFP_ATOMIC);
+	if (unlikely(!skb))
+		return;
+
+	info = IEEE80211_SKB_CB(skb);
 	memset(info, 0, sizeof(*info));
 
 	tid = skb->priority & IEEE80211_QOS_CTL_TAG1D_MASK;
-- 
2.35.1

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