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

[LinMa <linma@zju.edu.cn>]

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@kernel.org>
> Sent Time: 2021-07-22 02:26:20 (Thursday)
> To: "Lin Ma" <linma@zju.edu.cn>, "Marcel Holtmann" <marcel@holtmann.org>, "Johan Hedberg" <johan.hedberg@gmail.com>, "Luiz Augusto von Dentz" <luiz.dentz@gmail.com>
> Cc: linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org
> 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