netdev - [kernel PATCH v1] Bluetooth: L2CAP: Fix use-after-free

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Date: Wed, 24 May 2023 17:04:15 -0700
From: Zhengping Jiang <jiangzp@...gle.com>
To: linux-bluetooth@...r.kernel.org, marcel@...tmann.org, luiz.dentz@...il.com
Cc: chromeos-bluetooth-upstreaming@...omium.org, 
	Zhengping Jiang <jiangzp@...gle.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Johan Hedberg <johan.hedberg@...il.com>, Paolo Abeni <pabeni@...hat.com>, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: [kernel PATCH v1] Bluetooth: L2CAP: Fix use-after-free

Fix potential use-after-free in l2cap_le_command_rej.

Signed-off-by: Zhengping Jiang <jiangzp@...gle.com>
---

Changes in v1:
- Use l2cap_chan_hold_unless_zero to prevent adding refcnt when it is
  already 0.

 net/bluetooth/l2cap_core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 376b523c7b26..19b0b1f7ffed 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -6361,9 +6361,14 @@ static inline int l2cap_le_command_rej(struct l2cap_conn *conn,
 	if (!chan)
 		goto done;
 
+	chan = l2cap_chan_hold_unless_zero(chan);
+	if (!chan)
+		goto done;
+
 	l2cap_chan_lock(chan);
 	l2cap_chan_del(chan, ECONNREFUSED);
 	l2cap_chan_unlock(chan);
+	l2cap_chan_put(chan);
 
 done:
 	mutex_unlock(&conn->chan_lock);
-- 
2.40.1.698.g37aff9b760-goog