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linux/include/net/bluetooth
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Tetsuo Handa e04480920d Bluetooth: defer cleanup of resources in hci_unregister_dev() 
syzbot is hitting might_sleep() warning at hci_sock_dev_event() due to
calling lock_sock() with rw spinlock held [1].

It seems that history of this locking problem is a trial and error.

Commit b40df5743e ("[PATCH] bluetooth: fix socket locking in
hci_sock_dev_event()") in 2.6.21-rc4 changed bh_lock_sock() to
lock_sock() as an attempt to fix lockdep warning.

Then, commit 4ce61d1c7a ("[BLUETOOTH]: Fix locking in
hci_sock_dev_event().") in 2.6.22-rc2 changed lock_sock() to
local_bh_disable() + bh_lock_sock_nested() as an attempt to fix the
sleep in atomic context warning.

Then, commit 4b5dd696f8 ("Bluetooth: Remove local_bh_disable() from
hci_sock.c") in 3.3-rc1 removed local_bh_disable().

Then, commit e305509e67 ("Bluetooth: use correct lock to prevent UAF
of hdev object") in 5.13-rc5 again changed bh_lock_sock_nested() to
lock_sock() as an attempt to fix CVE-2021-3573.

This difficulty comes from current implementation that
hci_sock_dev_event(HCI_DEV_UNREG) is responsible for dropping all
references from sockets because hci_unregister_dev() immediately
reclaims resources as soon as returning from
hci_sock_dev_event(HCI_DEV_UNREG).

But the history suggests that hci_sock_dev_event(HCI_DEV_UNREG) was not
doing what it should do.

Therefore, instead of trying to detach sockets from device, let's accept
not detaching sockets from device at hci_sock_dev_event(HCI_DEV_UNREG),
by moving actual cleanup of resources from hci_unregister_dev() to
hci_cleanup_dev() which is called by bt_host_release() when all
references to this unregistered device (which is a kobject) are gone.

Since hci_sock_dev_event(HCI_DEV_UNREG) no longer resets
hci_pi(sk)->hdev, we need to check whether this device was unregistered
and return an error based on HCI_UNREGISTER flag.  There might be subtle
behavioral difference in "monitor the hdev" functionality; please report
if you found something went wrong due to this patch.

Link: https://syzkaller.appspot.com/bug?extid=a5df189917e79d5e59c9 [1]
Reported-by: syzbot <syzbot+a5df189917e79d5e59c9@syzkaller.appspotmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: e305509e67 ("Bluetooth: use correct lock to prevent UAF of hdev object")
Acked-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
History 2021-08-05 12:15:24 -07:00
..
bluetooth.h Bluetooth: btusb: Fix and detect most of the Chinese Bluetooth controllers 2020-07-28 09:09:00 +02:00
hci.h Bluetooth: Fix Set Extended (Scan Response) Data 2021-06-26 07:12:44 +02:00
hci_core.h Bluetooth: defer cleanup of resources in hci_unregister_dev() 2021-08-05 12:15:24 -07:00
hci_mon.h Bluetooth: monitor: Add support for ISO packets 2020-01-15 22:28:51 +01:00
hci_sock.h Bluetooth: Use only 8 bits for the HCI CMSG state flags 2020-06-12 15:10:46 +02:00
l2cap.h Bluetooth: L2CAP: Fix not checking for maximum number of DCID 2021-03-15 21:08:33 +01:00
mgmt.h Bluetooth: use inclusive language in SMP 2021-06-26 07:12:37 +02:00
rfcomm.h Bluetooth: Replace zero-length array with flexible-array member 2020-02-28 08:30:02 +01:00
sco.h Bluetooth: Add support for BT_PKT_STATUS CMSG data for SCO connections 2020-06-12 15:08:49 +02:00