When performing warm boot tests with an MT7920 device,
we encounter NULL pointer dereference 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@canonical.com>
---
 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

> When performing warm boot tests with an MT7920 device,
> we encounter NULL pointer dereference with failure rate 5/30.
…

                            dereferences?


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Regards,
Markus