Patch "Bluetooth: Fix l2cap_disconnect_req deadlock" has been added to the 4.14-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    Bluetooth: Fix l2cap_disconnect_req deadlock

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bluetooth-fix-l2cap_disconnect_req-deadlock.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 27a30f66df386d641b79f804350807a5a0340d74
Author: Ying Hsu <yinghsu@xxxxxxxxxxxx>
Date:   Wed May 31 03:44:56 2023 +0000

    Bluetooth: Fix l2cap_disconnect_req deadlock
    
    [ Upstream commit 02c5ea5246a44d6ffde0fddebfc1d56188052976 ]
    
    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@xxxxxxxxxxxx>
    Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index b0bb4cf52a7ee..281d1b375838a 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -4362,7 +4362,9 @@ 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);
 
@@ -4401,7 +4403,9 @@ 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);