[PATCH 5.16 0417/1017] Bluetooth: hci_serdev: call init_rwsem() before p->open()

From: Greg Kroah-Hartman
Date: Tue Apr 05 2022 - 08:04:41 EST

From: Pavel Skripkin <paskripkin@xxxxxxxxx>

[ Upstream commit 9d7cbe2b9cf5f650067df4f402fdd799d4bbb4e1 ]

kvartet reported, that hci_uart_tx_wakeup() uses uninitialized rwsem.
The problem was in wrong place for percpu_init_rwsem() call.

hci_uart_proto::open() may register a timer whose callback may call
hci_uart_tx_wakeup(). There is a chance, that hci_uart_register_device()
thread won't be fast enough to call percpu_init_rwsem().

Fix it my moving percpu_init_rwsem() call before p->open().

INFO: trying to register non-static key.
The code is fine but needs lockdep annotation, or maybe
you didn't initialize this object before use?
turning off the locking correctness validator.
CPU: 2 PID: 18524 Comm: syz-executor.5 Not tainted 5.16.0-rc6 #9
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
assign_lock_key kernel/locking/lockdep.c:951 [inline]
register_lock_class+0x148d/0x1950 kernel/locking/lockdep.c:1263
__lock_acquire+0x106/0x57e0 kernel/locking/lockdep.c:4906
lock_acquire kernel/locking/lockdep.c:5637 [inline]
lock_acquire+0x1ab/0x520 kernel/locking/lockdep.c:5602
percpu_down_read_trylock include/linux/percpu-rwsem.h:92 [inline]
hci_uart_tx_wakeup+0x12e/0x490 drivers/bluetooth/hci_ldisc.c:124
h5_timed_event+0x32f/0x6a0 drivers/bluetooth/hci_h5.c:188
call_timer_fn+0x1a5/0x6b0 kernel/time/timer.c:1421

Fixes: d73e17281665 ("Bluetooth: hci_serdev: Init hci_uart proto_lock to avoid oops")
Reported-by: Yiru Xu <xyru1999@xxxxxxxxx>
Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx>
Signed-off-by: Marcel Holtmann <marcel@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/bluetooth/hci_serdev.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/hci_serdev.c b/drivers/bluetooth/hci_serdev.c
index 3b00d82d36cf..4cda890ce647 100644
--- a/drivers/bluetooth/hci_serdev.c
+++ b/drivers/bluetooth/hci_serdev.c
@@ -305,6 +305,8 @@ int hci_uart_register_device(struct hci_uart *hu,
if (err)
return err;

+ percpu_init_rwsem(&hu->proto_lock);
err = p->open(hu);
if (err)
goto err_open;
@@ -327,7 +329,6 @@ int hci_uart_register_device(struct hci_uart *hu,

INIT_WORK(&hu->init_ready, hci_uart_init_work);
INIT_WORK(&hu->write_work, hci_uart_write_work);
- percpu_init_rwsem(&hu->proto_lock);

/* Only when vendor specific setup callback is provided, consider
* the manufacturer information valid. This avoids filling in the