Hi Luiz, > use-after-free error in lock_sock_nested is reported: > > [ 179.140137][ T3731] ===================================================== > [ 179.142675][ T3731] BUG: KMSAN: use-after-free in lock_sock_nested+0x280/0x2c0 > [ 179.145494][ T3731] CPU: 4 PID: 3731 Comm: kworker/4:2 Not tainted 5.12.0-rc6+ #54 > [ 179.148432][ T3731] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 > [ 179.151806][ T3731] Workqueue: events l2cap_chan_timeout > [ 179.152730][ T3731] Call Trace: > [ 179.153301][ T3731] dump_stack+0x24c/0x2e0 > [ 179.154063][ T3731] kmsan_report+0xfb/0x1e0 > [ 179.154855][ T3731] __msan_warning+0x5c/0xa0 > [ 179.155579][ T3731] lock_sock_nested+0x280/0x2c0 > [ 179.156436][ T3731] ? kmsan_get_metadata+0x116/0x180 > [ 179.157257][ T3731] l2cap_sock_teardown_cb+0xb8/0x890 > [ 179.158154][ T3731] ? __msan_metadata_ptr_for_load_8+0x10/0x20 > [ 179.159141][ T3731] ? kmsan_get_metadata+0x116/0x180 > [ 179.159994][ T3731] ? kmsan_get_shadow_origin_ptr+0x84/0xb0 > [ 179.160959][ T3731] ? l2cap_sock_recv_cb+0x420/0x420 > [ 179.161834][ T3731] l2cap_chan_del+0x3e1/0x1d50 > [ 179.162608][ T3731] ? kmsan_get_metadata+0x116/0x180 > [ 179.163435][ T3731] ? kmsan_get_shadow_origin_ptr+0x84/0xb0 > [ 179.164406][ T3731] l2cap_chan_close+0xeea/0x1050 > [ 179.165189][ T3731] ? kmsan_internal_unpoison_shadow+0x42/0x70 > [ 179.166180][ T3731] l2cap_chan_timeout+0x1da/0x590 > [ 179.167066][ T3731] ? __msan_metadata_ptr_for_load_8+0x10/0x20 > [ 179.168023][ T3731] ? l2cap_chan_create+0x560/0x560 > [ 179.168818][ T3731] process_one_work+0x121d/0x1ff0 > [ 179.169598][ T3731] worker_thread+0x121b/0x2370 > [ 179.170346][ T3731] kthread+0x4ef/0x610 > [ 179.171010][ T3731] ? process_one_work+0x1ff0/0x1ff0 > [ 179.171828][ T3731] ? kthread_blkcg+0x110/0x110 > [ 179.172587][ T3731] ret_from_fork+0x1f/0x30 > [ 179.173348][ T3731] > [ 179.173752][ T3731] Uninit was created at: > [ 179.174409][ T3731] kmsan_internal_poison_shadow+0x5c/0xf0 > [ 179.175373][ T3731] kmsan_slab_free+0x76/0xc0 > [ 179.176060][ T3731] kfree+0x3a5/0x1180 > [ 179.176664][ T3731] __sk_destruct+0x8af/0xb80 > [ 179.177375][ T3731] __sk_free+0x812/0x8c0 > [ 179.178032][ T3731] sk_free+0x97/0x130 > [ 179.178686][ T3731] l2cap_sock_release+0x3d5/0x4d0 > [ 179.179457][ T3731] sock_close+0x150/0x450 > [ 179.180117][ T3731] __fput+0x6bd/0xf00 > [ 179.180787][ T3731] ____fput+0x37/0x40 > [ 179.181481][ T3731] task_work_run+0x140/0x280 > [ 179.182219][ T3731] do_exit+0xe51/0x3e60 > [ 179.182930][ T3731] do_group_exit+0x20e/0x450 > [ 179.183656][ T3731] get_signal+0x2dfb/0x38f0 > [ 179.184344][ T3731] arch_do_signal_or_restart+0xaa/0xe10 > [ 179.185266][ T3731] exit_to_user_mode_prepare+0x2d2/0x560 > [ 179.186136][ T3731] syscall_exit_to_user_mode+0x35/0x60 > [ 179.186984][ T3731] do_syscall_64+0xc5/0x140 > [ 179.187681][ T3731] entry_SYSCALL_64_after_hwframe+0x44/0xae > [ 179.188604][ T3731] ===================================================== > > In our case, there are two Thread A and B: > > Context: Thread A: Context: Thread B: > > l2cap_chan_timeout() __se_sys_shutdown() > l2cap_chan_close() l2cap_sock_shutdown() > l2cap_chan_del() l2cap_chan_close() > l2cap_sock_teardown_cb() l2cap_sock_teardown_cb() > > Once l2cap_sock_teardown_cb() excuted, this sock will be marked as SOCK_ZAPPED, > and can be treated as killable in l2cap_sock_kill() if sock_orphan() has > excuted, at this time we close sock through sock_close() which end to call > l2cap_sock_kill() like Thread C: > > Context: Thread C: > > sock_close() > l2cap_sock_release() > sock_orphan() > l2cap_sock_kill() #free sock if refcnt is 1 > > If C completed, Once A or B reaches l2cap_sock_teardown_cb() again, > use-after-free happened. > > We should set chan->data to NULL if sock is destructed, for telling teardown > operation is not allowed in l2cap_sock_teardown_cb(), and also we should > avoid killing an already killed socket in l2cap_sock_close_cb(). > > Signed-off-by: Wang ShaoBo <bobo.shaobowang@xxxxxxxxxx> > Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx> > --- > net/bluetooth/l2cap_sock.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) patch has been applied to bluetooth-next tree. Regards Marcel
