Hi Jiri
Thanks for the concern. In fact, the discussion over this issue has been several weeks, and we welcome new thoughts.
> From: "Jiri Kosina" <jikos@xxxxxxxxxx>
> Sent Time: 2021-07-22 02:26:20 (Thursday)
> To: "Lin Ma" <linma@xxxxxxxxxx>, "Marcel Holtmann" <marcel@xxxxxxxxxxxx>, "Johan Hedberg" <johan.hedberg@xxxxxxxxx>, "Luiz Augusto von Dentz" <luiz.dentz@xxxxxxxxx>
> Cc: linux-bluetooth@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: Two issues caused by commit e305509e678b3 ("Bluetooth: use correct lock to prevent UAF of hdev object")
>
> 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.
>
The details of this UAF can be found at oss: https://www.openwall.com/lists/oss-security/2021/06/08/2
And you can follow some existing discussions at:
https://www.spinics.net/lists/linux-bluetooth/msg92649.html
https://marc.info/?l=linux-bluetooth&m=162441276805113&w=2
https://marc.info/?l=linux-bluetooth&m=162653675414330&w=2
Hope this can help you to understand the problem we are confronting.
Thanks
Lin Ma
> >
> >
> >
> > (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
