Re: Two issues caused by commit e305509e678b3 ("Bluetooth: use correct lock to prevent UAF of hdev object")

From: Jiri Kosina
Date: Wed Jul 21 2021 - 14:26:27 EST

On Tue, 13 Jul 2021, Jiri Kosina wrote:

> Hi,
>
> commit e305509e678b3 ("Bluetooth: use correct lock to prevent UAF of hdev
> object") has two issues, and I believe it should be reverted for 5.14
> final. Could you please elaborate what is the exact UAF scenario the patch
> is fixing? It's rather hard to deduce from the very short changelog, but
> it's pretty obvious that it creates at least two issues.

Marcel, Johan, Luiz, any thoughts on this please? Thanks.

>
>
>
> (1) it introduces a possibility of deadlock between hci_sock_dev_event()
> and hci_sock_sendmsg().
>
> Namely:
>
> - hci_sock_sendmsg(HCI_CHANNEL_LOGGING) acquires lock_sock(sk) and then
> calls into hci_logging_frame() -> hci_send_to_channel() which in turn
> acquires hci_sk_list.lock
>
> - after the mentioned commit, hci_sock_dev_event() first acquires
> hci_sk_list.lock before doing lock_sock(sk) on each of the sockets it
> iterates through, creating the reverse dependency
>
>
> Please find the full lockdep report below for reference.
>
> (2) it causes sleeping function to be called from atomic context, because
> it's not allowed to sleep after acquiring read_lock(), which is exactly
> what this patch does (lock_sock() is sleepable). Report below as well.
>
>
>
>
>
>
> BUG: sleeping function called from invalid context at net/core/sock.c:3100
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 448, name: kworker/0:5
> 6 locks held by kworker/0:5/448:
> #0: ffff89e947fb4338 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x1c2/0x5e0
> #1: ffffadef40973e78 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x1c2/0x5e0
> #2: ffff89e946998a20 (&dev->mutex){....}-{3:3}, at: hub_event+0x6a/0xd50 [usbcore]
> #3: ffff89e950828a20 (&dev->mutex){....}-{3:3}, at: usb_disconnect+0x54/0x270 [usbcore]
> #4: ffff89e9504e71a8 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0x1a/0x1d0
> #5: ffffffffc117a3c0 (hci_sk_list.lock){++++}-{2:2}, at: hci_sock_dev_event+0x12b/0x1e0 [bluetooth]
> CPU: 0 PID: 448 Comm: kworker/0:5 Not tainted 5.14.0-rc1-00003-g7fef2edf7cc7 #15
> Hardware name: LENOVO 20K5S22R00/20K5S22R00, BIOS R0IET38W (1.16 ) 05/31/2017
> Workqueue: usb_hub_wq hub_event [usbcore]
> Call Trace:
> dump_stack_lvl+0x56/0x6c
> ___might_sleep+0x1b6/0x210
> lock_sock_nested+0x29/0xa0
> hci_sock_dev_event+0x156/0x1e0 [bluetooth]
> hci_unregister_dev+0xd2/0x350 [bluetooth]
> btusb_disconnect+0x63/0x150 [btusb]
> usb_unbind_interface+0x79/0x260 [usbcore]
> device_release_driver_internal+0xf7/0x1d0
> bus_remove_device+0xef/0x160
> device_del+0x1ac/0x430
> ? usb_remove_ep_devs+0x1b/0x30 [usbcore]
> usb_disable_device+0x8d/0x1a0 [usbcore]
> usb_disconnect+0xc1/0x270 [usbcore]
> ? hub_event+0x4b0/0xd50 [usbcore]
> hub_port_connect+0x82/0xa20 [usbcore]
> ? __mutex_unlock_slowpath+0x43/0x2b0
> hub_event+0x4c4/0xd50 [usbcore]
> ? lock_is_held_type+0xb4/0x120
> process_one_work+0x244/0x5e0
> worker_thread+0x3c/0x390
> ? process_one_work+0x5e0/0x5e0
> kthread+0x133/0x160
> ? set_kthread_struct+0x40/0x40
> ret_from_fork+0x22/0x30
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.14.0-rc1-00003-g7fef2edf7cc7 #15 Tainted: G W
> ------------------------------------------------------
> kworker/0:5/448 is trying to acquire lock:
> ffff89e950647920 (sk_lock-AF_BLUETOOTH-BTPROTO_HCI){+.+.}-{0:0}, at: hci_sock_dev_event+0x156/0x1e0 [bluetooth]
>
> but task is already holding lock:
> ffffffffc117a3c0 (hci_sk_list.lock){++++}-{2:2}, at: hci_sock_dev_event+0x12b/0x1e0 [bluetooth]
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #1 (hci_sk_list.lock){++++}-{2:2}:
> _raw_read_lock+0x38/0x70
> systemd-sysv-generator[1254]: stat() failed on /etc/init.d/jexec, ignoring: No such file or directory
> hci_send_to_channel+0x22/0x50 [bluetooth]
> hci_sock_sendmsg+0xa2b/0xa40 [bluetooth]
> sock_sendmsg+0x5b/0x60
> ____sys_sendmsg+0x1ed/0x250
> systemd-sysv-generator[1254]: SysV service '/etc/init.d/tpfand' lacks a native systemd unit file. Automatically generating a unit file for compatibility. Please update package to include a native systemd unit file, in order to make it more safe and robust.
> ___sys_sendmsg+0x88/0xd0
> __sys_sendmsg+0x5e/0xa0
> do_syscall_64+0x3a/0xb0
> systemd-sysv-generator[1254]: SysV service '/etc/init.d/boot.local' lacks a native systemd unit file. Automatically generating a unit file for compatibility. Please update package to include a native systemd unit file, in order to make it more safe and robust.
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> -> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_HCI){+.+.}-{0:0}:
> __lock_acquire+0x124a/0x1680
> lock_acquire+0x278/0x300
> lock_sock_nested+0x72/0xa0
> hci_sock_dev_event+0x156/0x1e0 [bluetooth]
> hci_unregister_dev+0xd2/0x350 [bluetooth]
> btusb_disconnect+0x63/0x150 [btusb]
> usb_unbind_interface+0x79/0x260 [usbcore]
> device_release_driver_internal+0xf7/0x1d0
> bus_remove_device+0xef/0x160
> device_del+0x1ac/0x430
> usb_disable_device+0x8d/0x1a0 [usbcore]
> usb_disconnect+0xc1/0x270 [usbcore]
> hub_port_connect+0x82/0xa20 [usbcore]
> hub_event+0x4c4/0xd50 [usbcore]
> process_one_work+0x244/0x5e0
> worker_thread+0x3c/0x390
> kthread+0x133/0x160
> ret_from_fork+0x22/0x30
>
> other info that might help us debug this:
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(hci_sk_list.lock);
> lock(sk_lock-AF_BLUETOOTH-BTPROTO_HCI);
> lock(hci_sk_list.lock);
> lock(sk_lock-AF_BLUETOOTH-BTPROTO_HCI);
>
> *** DEADLOCK ***
>
> 6 locks held by kworker/0:5/448:
> #0: ffff89e947fb4338 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x1c2/0x5e0
> #1: ffffadef40973e78 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x1c2/0x5e0
> #2: ffff89e946998a20 (&dev->mutex){....}-{3:3}, at: hub_event+0x6a/0xd50 [usbcore]
> #3: ffff89e950828a20 (&dev->mutex){....}-{3:3}, at: usb_disconnect+0x54/0x270 [usbcore]
> #4: ffff89e9504e71a8 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0x1a/0x1d0
> #5: ffffffffc117a3c0 (hci_sk_list.lock){++++}-{2:2}, at: hci_sock_dev_event+0x12b/0x1e0 [bluetooth]
>
> stack backtrace:
> CPU: 0 PID: 448 Comm: kworker/0:5 Tainted: G W 5.14.0-rc1-00003-g7fef2edf7cc7 #15
> Hardware name: LENOVO 20K5S22R00/20K5S22R00, BIOS R0IET38W (1.16 ) 05/31/2017
> Workqueue: usb_hub_wq hub_event [usbcore]
> Call Trace:
> dump_stack_lvl+0x56/0x6c
> check_noncircular+0x105/0x120
> ? stack_trace_save+0x4b/0x70
> ? save_trace+0x3d/0x340
> ? __lock_acquire+0x124a/0x1680
> __lock_acquire+0x124a/0x1680
> lock_acquire+0x278/0x300
> ? hci_sock_dev_event+0x156/0x1e0 [bluetooth]
> ? lock_release+0x15a/0x2a0
> lock_sock_nested+0x72/0xa0
> ? hci_sock_dev_event+0x156/0x1e0 [bluetooth]
> hci_sock_dev_event+0x156/0x1e0 [bluetooth]
> hci_unregister_dev+0xd2/0x350 [bluetooth]
> btusb_disconnect+0x63/0x150 [btusb]
> usb_unbind_interface+0x79/0x260 [usbcore]
> device_release_driver_internal+0xf7/0x1d0
> bus_remove_device+0xef/0x160
> device_del+0x1ac/0x430
> ? usb_remove_ep_devs+0x1b/0x30 [usbcore]
> usb_disable_device+0x8d/0x1a0 [usbcore]
> usb_disconnect+0xc1/0x270 [usbcore]
> ? hub_event+0x4b0/0xd50 [usbcore]
> hub_port_connect+0x82/0xa20 [usbcore]
> ? __mutex_unlock_slowpath+0x43/0x2b0
> hub_event+0x4c4/0xd50 [usbcore]
> ? lock_is_held_type+0xb4/0x120
> process_one_work+0x244/0x5e0
> worker_thread+0x3c/0x390
> ? process_one_work+0x5e0/0x5e0
> kthread+0x133/0x160
> ? set_kthread_struct+0x40/0x40
> ret_from_fork+0x22/0x30
>
>
>
> --
> Jiri Kosina
> SUSE Labs
>

--
Jiri Kosina
SUSE Labs