netdev - [PATCH v4] Bluetooth: Fix l2cap_disconnect

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20230531023821.349759-1-yinghsu@chromium.org>
Date: Wed, 31 May 2023 02:38:16 +0000
From: Ying Hsu <yinghsu@...omium.org>
To: linux-bluetooth@...r.kernel.org
Cc: chromeos-bluetooth-upstreaming@...omium.org,
	Ying Hsu <yinghsu@...omium.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Johan Hedberg <johan.hedberg@...il.com>,
	Luiz Augusto von Dentz <luiz.dentz@...il.com>,
	Marcel Holtmann <marcel@...tmann.org>,
	Paolo Abeni <pabeni@...hat.com>,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: [PATCH v4] Bluetooth: Fix l2cap_disconnect_req deadlock

L2CAP assumes that the locks conn->chan_lock and chan->lock are
acquired in the order conn->chan_lock, chan->lock to avoid
potential deadlock.
For example, l2sock_shutdown acquires these locks in the order:
  mutex_lock(&conn->chan_lock)
  l2cap_chan_lock(chan)

However, l2cap_disconnect_req acquires chan->lock in
l2cap_get_chan_by_scid first and then acquires conn->chan_lock
before calling l2cap_chan_del. This means that these locks are
acquired in unexpected order, which leads to potential deadlock:
  l2cap_chan_lock(c)
  mutex_lock(&conn->chan_lock)

This patch releases chan->lock before acquiring the conn_chan_lock
to avoid the potential deadlock.

Fixes: ("a2a9339e1c9d Bluetooth: L2CAP: Fix use-after-free in l2cap_disconnect_{req,rsp}")
Signed-off-by: Ying Hsu <yinghsu@...omium.org>
---
This commit has been tested on a Chromebook device.

Changes in v4:
- Using l2cap_get_chan_by_scid to avoid repeated code.
- Releasing chan->lock before acquiring conn->chan_lock.

Changes in v3:
- Adding the fixes tag.

Changes in v2:
- Adding the prefix "Bluetooth:" to subject line.

 net/bluetooth/l2cap_core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 376b523c7b26..d9c4d26b2518 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -4663,7 +4663,9 @@ static inline int l2cap_disconnect_req(struct l2cap_conn *conn,
 
 	chan->ops->set_shutdown(chan);
 
+	l2cap_chan_unlock(chan);
 	mutex_lock(&conn->chan_lock);
+	l2cap_chan_lock(chan);
 	l2cap_chan_del(chan, ECONNRESET);
 	mutex_unlock(&conn->chan_lock);
 
@@ -4702,7 +4704,9 @@ static inline int l2cap_disconnect_rsp(struct l2cap_conn *conn,
 		return 0;
 	}
 
+	l2cap_chan_unlock(chan);
 	mutex_lock(&conn->chan_lock);
+	l2cap_chan_lock(chan);
 	l2cap_chan_del(chan, 0);
 	mutex_unlock(&conn->chan_lock);
 
-- 
2.41.0.rc0.172.g3f132b7071-goog