[PATCH 5.12 448/677] Bluetooth: avoid deadlock between hci_dev->lock and socket lock

From: Greg Kroah-Hartman
Date: Wed May 12 2021 - 14:58:17 EST

From: Jiri Kosina <jkosina@xxxxxxx>

[ Upstream commit 17486960d79b900c45e0bb8fbcac0262848582ba ]

Commit eab2404ba798 ("Bluetooth: Add BT_PHY socket option") added a
dependency between socket lock and hci_dev->lock that could lead to
deadlock.

It turns out that hci_conn_get_phy() is not in any way relying on hdev
being immutable during the runtime of this function, neither does it even
look at any of the members of hdev, and as such there is no need to hold
that lock.

This fixes the lockdep splat below:

======================================================
WARNING: possible circular locking dependency detected
5.12.0-rc1-00026-g73d464503354 #10 Not tainted
------------------------------------------------------
bluetoothd/1118 is trying to acquire lock:
ffff8f078383c078 (&hdev->lock){+.+.}-{3:3}, at: hci_conn_get_phy+0x1c/0x150 [bluetooth]

but task is already holding lock:
ffff8f07e831d920 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+.}-{0:0}, at: l2cap_sock_getsockopt+0x8b/0x610

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+.}-{0:0}:
lock_sock_nested+0x72/0xa0
l2cap_sock_ready_cb+0x18/0x70 [bluetooth]
l2cap_config_rsp+0x27a/0x520 [bluetooth]
l2cap_sig_channel+0x658/0x1330 [bluetooth]
l2cap_recv_frame+0x1ba/0x310 [bluetooth]
hci_rx_work+0x1cc/0x640 [bluetooth]
process_one_work+0x244/0x5f0
worker_thread+0x3c/0x380
kthread+0x13e/0x160
ret_from_fork+0x22/0x30

-> #2 (&chan->lock#2/1){+.+.}-{3:3}:
__mutex_lock+0xa3/0xa10
l2cap_chan_connect+0x33a/0x940 [bluetooth]
l2cap_sock_connect+0x141/0x2a0 [bluetooth]
__sys_connect+0x9b/0xc0
__x64_sys_connect+0x16/0x20
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #1 (&conn->chan_lock){+.+.}-{3:3}:
__mutex_lock+0xa3/0xa10
l2cap_chan_connect+0x322/0x940 [bluetooth]
l2cap_sock_connect+0x141/0x2a0 [bluetooth]
__sys_connect+0x9b/0xc0
__x64_sys_connect+0x16/0x20
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (&hdev->lock){+.+.}-{3:3}:
__lock_acquire+0x147a/0x1a50
lock_acquire+0x277/0x3d0
__mutex_lock+0xa3/0xa10
hci_conn_get_phy+0x1c/0x150 [bluetooth]
l2cap_sock_getsockopt+0x5a9/0x610 [bluetooth]
__sys_getsockopt+0xcc/0x200
__x64_sys_getsockopt+0x20/0x30
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae

other info that might help us debug this:

Chain exists of:
&hdev->lock --> &chan->lock#2/1 --> sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP);
lock(&chan->lock#2/1);
lock(sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP);
lock(&hdev->lock);

*** DEADLOCK ***

1 lock held by bluetoothd/1118:
#0: ffff8f07e831d920 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+.}-{0:0}, at: l2cap_sock_getsockopt+0x8b/0x610 [bluetooth]

stack backtrace:
CPU: 3 PID: 1118 Comm: bluetoothd Not tainted 5.12.0-rc1-00026-g73d464503354 #10
Hardware name: LENOVO 20K5S22R00/20K5S22R00, BIOS R0IET38W (1.16 ) 05/31/2017
Call Trace:
dump_stack+0x7f/0xa1
check_noncircular+0x105/0x120
? __lock_acquire+0x147a/0x1a50
__lock_acquire+0x147a/0x1a50
lock_acquire+0x277/0x3d0
? hci_conn_get_phy+0x1c/0x150 [bluetooth]
? __lock_acquire+0x2e1/0x1a50
? lock_is_held_type+0xb4/0x120
? hci_conn_get_phy+0x1c/0x150 [bluetooth]
__mutex_lock+0xa3/0xa10
? hci_conn_get_phy+0x1c/0x150 [bluetooth]
? lock_acquire+0x277/0x3d0
? mark_held_locks+0x49/0x70
? mark_held_locks+0x49/0x70
? hci_conn_get_phy+0x1c/0x150 [bluetooth]
hci_conn_get_phy+0x1c/0x150 [bluetooth]
l2cap_sock_getsockopt+0x5a9/0x610 [bluetooth]
__sys_getsockopt+0xcc/0x200
__x64_sys_getsockopt+0x20/0x30
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7fb73df33eee
Code: 48 8b 0d 85 0f 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 49 89 ca b8 37 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 52 0f 0c 00 f7 d8 64 89 01 48
RSP: 002b:00007fffcfbbbf08 EFLAGS: 00000203 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 0000000000000019 RCX: 00007fb73df33eee
RDX: 000000000000000e RSI: 0000000000000112 RDI: 0000000000000018
RBP: 0000000000000000 R08: 00007fffcfbbbf44 R09: 0000000000000000
R10: 00007fffcfbbbf3c R11: 0000000000000203 R12: 0000000000000000
R13: 0000000000000018 R14: 0000000000000000 R15: 0000556fcefc70d0

Fixes: eab2404ba798 ("Bluetooth: Add BT_PHY socket option")
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
Signed-off-by: Marcel Holtmann <marcel@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/bluetooth/hci_conn.c | 4 ----
1 file changed, 4 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 6ffa89e3ba0a..f72646690539 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1830,8 +1830,6 @@ u32 hci_conn_get_phy(struct hci_conn *conn)
{
u32 phys = 0;

- hci_dev_lock(conn->hdev);
-
/* BLUETOOTH CORE SPECIFICATION Version 5.2 | Vol 2, Part B page 471:
* Table 6.2: Packets defined for synchronous, asynchronous, and
* CSB logical transport types.
@@ -1928,7 +1926,5 @@ u32 hci_conn_get_phy(struct hci_conn *conn)
break;
}

- hci_dev_unlock(conn->hdev);
-
return phys;
}
--
2.30.2