CVE-2026-80666

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

Bluetooth: sco: Fix a race condition in sco_sock_timeout()

sco_sock_timeout() runs asynchronously and lock_sock(sk). If the socket
is closing while the timer is running, it holds the same lock
(lock_sock(sk)) twice, leading to a deadlock.

CPU 0                      CPU 1
====================       ======================
sco_sock_close()
                           sco_sock_timeout()
lock_sock(sk) // <-- LOCK
  __sco_sock_close()
    sco_chan_del()
      sco_conn_put()
	      sco_conn_free()
	        disable_delayed_work_sync()
	                           lock(sk) // <-- SAME LOCK

Fix this by moving disable_delayed_work_sync() outside of lock_sock(sk),
ensuring that no lock_sock(sk) is held before sco_sock_timeout().

Lockdep splat:

WARNING: possible circular locking dependency detected
6.13.0-rc4 #7 Not tainted

syz-executor292/9514 is trying to acquire lock:
ffff8881115d5070 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: rcu_lock_acquire sect/v6.13-rc4/./include/linux/rcupdate.h:337 [inline]
ffff8881115d5070 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: rcu_read_lock sect/v6.13-rc4/./include/linux/rcupdate.h:849 [inline]
ffff8881115d5070 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: start_flush_work sect/v6.13-rc4/kernel/workqueue.c:4137 [inline]
ffff8881115d5070 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: __flush_work+0xd1/0xc40 sect/v6.13-rc4/kernel/workqueue.c:4195

but task is already holding lock:
ffff88807db3a258 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: lock_sock sect/v6.13-rc4/./include/net/sock.h:1623 [inline]
ffff88807db3a258 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: sco_sock_close+0x25/0x100 sect/v6.13-rc4/net/bluetooth/sco.c:524

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
       lock_acquire+0x1c4/0x520 sect/v6.13-rc4/kernel/locking/lockdep.c:5849
       lock_sock_nested+0x48/0x130 sect/v6.13-rc4/net/core/sock.c:3622
       lock_sock sect/v6.13-rc4/./include/net/sock.h:1623 [inline]
       sco_sock_timeout+0xbe/0x270 sect/v6.13-rc4/net/bluetooth/sco.c:158
       process_one_work sect/v6.13-rc4/kernel/workqueue.c:3229 [inline]
       process_scheduled_works+0xa99/0x18f0 sect/v6.13-rc4/kernel/workqueue.c:3310
       worker_thread+0x8a9/0xd80 sect/v6.13-rc4/kernel/workqueue.c:3391
       kthread+0x2c6/0x360 sect/v6.13-rc4/kernel/kthread.c:389
       ret_from_fork+0x4e/0x80 sect/v6.13-rc4/arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 sect/v6.13-rc4/arch/x86/entry/entry_64.S:244

-> #0 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}:
       check_prev_add sect/v6.13-rc4/kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add sect/v6.13-rc4/kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x1888/0x5760 sect/v6.13-rc4/kernel/locking/lockdep.c:3904
       __lock_acquire+0x13b4/0x2120 sect/v6.13-rc4/kernel/locking/lockdep.c:5226
       lock_acquire+0x1c4/0x520 sect/v6.13-rc4/kernel/locking/lockdep.c:5849
       touch_work_lockdep_map sect/v6.13-rc4/kernel/workqueue.c:3909 [inline]
       start_flush_work sect/v6.13-rc4/kernel/workqueue.c:4163 [inline]
       __flush_work+0x70f/0xc40 sect/v6.13-rc4/kernel/workqueue.c:4195
       __cancel_work_sync sect/v6.13-rc4/kernel/workqueue.c:4351 [inline]
       disable_delayed_work_sync+0xbb/0xf0 sect/v6.13-rc4/kernel/workqueue.c:4514
       sco_conn_free sect/v6.13-rc4/net/bluetooth/sco.c:95 [inline]
       kref_put sect/v6.13-rc4/./include/linux/kref.h:65 [inline]
       sco_conn_put+0x18f/0x270 sect/v6.13-rc4/net/bluetooth/sco.c:107
       sco_chan_del+0xe2/0x210 sect/v6.13-rc4/net/bluetooth/sco.c:236
       sco_sock_close+0x8f/0x100 sect/v6.13-rc4/net/bluetooth/sco.c:526
       sco_sock_release+0x62/0x2d0 sect/v6.13-rc4/net/blueto
---truncated---