In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: use chan timer to close channels in cleanup_listen() l2cap_chan_close() removes the channel from conn->chan_l, which must be done under conn->lock

Overview

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: L2CAP: use chan timer to close channels in cleanup_listen()

l2cap_chan_close() removes the channel from conn->chan_l, which must be done under conn->lock. cleanup_listen() runs under the parent sk_lock, so acquiring conn->lock would invert the established conn->lock -> chan->lock -> sk_lock order.

Instead of calling l2cap_chan_close() directly, schedule l2cap_chan_timeout with delay 0 to close the channel asynchronously. The timeout handler already acquires conn->lock and chan->lock in the correct order.

The timer is only armed when chan->conn is still set: if it is already NULL, l2cap_conn_del() has already processed this channel (l2cap_chan_del + l2cap_sock_teardown_cb + l2cap_sock_close_cb), so there is nothing left to do. If l2cap_conn_del() races in after the timer is armed, __clear_chan_timer() inside l2cap_chan_del() cancels it; if the timer has already fired, the handler returns harmlessly because chan->conn was cleared.

Affected

• linux_kernel >= 3.4, < 5.10.259
• linux_kernel >= 5.11, < 5.15.210
• linux_kernel >= 5.16, < 6.1.176
• linux_kernel >= 6.2, < 6.6.143
• linux_kernel >= 6.7, < 6.12.93
• linux_kernel >= 6.13, < 6.18.35
• linux_kernel >= 6.19, < 7.0.12
• linux_kernel = 7.1

Remediation

Upgrade past the affected range:

• linux_kernel 7.0.12