Bluetooth: Fix l2cap_disconnect_req deadlock
authorYing Hsu <yinghsu@chromium.org>
Wed, 31 May 2023 03:44:56 +0000 (03:44 +0000)
committerLuiz Augusto von Dentz <luiz.von.dentz@intel.com>
Tue, 6 Jun 2023 00:13:14 +0000 (17:13 -0700)
commit02c5ea5246a44d6ffde0fddebfc1d56188052976
treef738f7a76be161ed2cce14b3b459fbadb50bb984
parent47c5d829a3e326b7395352a10fc8a6effe7afa15
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@chromium.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
net/bluetooth/l2cap_core.c