linux-kernel - [PATCH v2] Bluetooth: btusb: Add NULL check for data in btusb

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Message-ID: <20241223094411.47496-1-en-wei.wu@canonical.com>
Date: Mon, 23 Dec 2024 17:44:10 +0800
From: En-Wei Wu <en-wei.wu@...onical.com>
To: marcel@...tmann.org,
	luiz.dentz@...il.com,
	linux-bluetooth@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Markus.Elfring@....de
Subject: [PATCH v2] Bluetooth: btusb: Add NULL check for data in btusb_suspend

When performing warm boot tests with an MT7920 device, we encounter
NULL pointer dereferences with failure rate 5/30. The crash occurs
during device suspend when btusb attempts to access data->hdev where
data is NULL. This may happen due to a race condition between PM suspend
and device disconnect. The root cause needs further investigation.

BUG: kernel NULL pointer dereference, address: 0000000000000000
Workqueue: pm pm_runtime_work
RIP: 0010:btusb_suspend+0x1d/0x1d0 [btusb]

Add a NULL check for data and return -ENODEV in this case to prevent
the NULL pointer dereference. This indicates that the device is no
longer available, which is appropriate when the driver's private data
is missing.

Signed-off-by: En-Wei Wu <en-wei.wu@...onical.com>
---
Changes in v2:
- Change "dereference" to "dereferences" in commit message
- Re-flow commit message lines to use more characters per line

 drivers/bluetooth/btusb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index 279fe6c115fa..a0461528548b 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -4096,6 +4096,9 @@ static int btusb_suspend(struct usb_interface *intf, pm_message_t message)

 	BT_DBG("intf %p", intf);

+	if (!data)
+		return -ENODEV;
+
 	/* Don't auto-suspend if there are connections; external suspend calls
 	 * shall never fail.
 	 */
-- 
2.43.0