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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Yiru Xu <xyru1999@gmail.com>,
        Pavel Skripkin <paskripkin@gmail.com>,
        Marcel Holtmann <marcel@holtmann.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 117/338] Bluetooth: hci_serdev: call init_rwsem() before p->open()
Date:   Thu, 14 Apr 2022 15:10:20 +0200
Message-Id: <20220414110842.237202671@linuxfoundation.org>
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From: Pavel Skripkin <paskripkin@gmail.com>

[ 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:
 <IRQ>
 __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@gmail.com>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 7b3aade431e5..9ebcf0d9e395 100644
--- a/drivers/bluetooth/hci_serdev.c
+++ b/drivers/bluetooth/hci_serdev.c
@@ -288,6 +288,8 @@ 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;
@@ -310,7 +312,6 @@ 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
-- 
2.34.1