linux-kernel - [PATCH] media: hdpvr: call flush

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Date:   Thu, 17 Feb 2022 12:39:40 +0800
From:   Dongliang Mu <dzm91@...t.edu.cn>
To:     Hans Verkuil <hverkuil@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Dongliang Mu <mudongliangabcd@...il.com>
Cc:     syzkaller <syzkaller@...glegroups.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] media: hdpvr: call flush_work only if initialized

From: Dongliang Mu <mudongliangabcd@...il.com>

flush_work will throw one WARN if worker->func is NULL. So we should always
initialize one worker before calling flush_work. When hdpvr_probe does not
initialize its worker, the hdpvr_disconnect will encounter one WARN. The
stack trace is in the following:

 hdpvr_disconnect+0xb8/0xf2 drivers/media/usb/hdpvr/hdpvr-core.c:425
 usb_unbind_interface+0xbf/0x3a0 drivers/usb/core/driver.c:458
 __device_release_driver drivers/base/dd.c:1206 [inline]
 device_release_driver_internal+0x22a/0x230 drivers/base/dd.c:1237
 bus_remove_device+0x108/0x160 drivers/base/bus.c:529
 device_del+0x1fe/0x510 drivers/base/core.c:3592
 usb_disable_device+0xd1/0x1d0 drivers/usb/core/message.c:1419
 usb_disconnect+0x109/0x330 drivers/usb/core/hub.c:2228

Fix this by adding a sanity check of the worker before flush_work.

Reported-by: syzkaller <syzkaller@...glegroups.com>
Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
---
 drivers/media/usb/hdpvr/hdpvr-core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/hdpvr/hdpvr-core.c b/drivers/media/usb/hdpvr/hdpvr-core.c
index 52e05a69c46e..d102b459d45d 100644
--- a/drivers/media/usb/hdpvr/hdpvr-core.c
+++ b/drivers/media/usb/hdpvr/hdpvr-core.c
@@ -422,7 +422,8 @@ static void hdpvr_disconnect(struct usb_interface *interface)
 	mutex_unlock(&dev->io_mutex);
 	v4l2_device_disconnect(&dev->v4l2_dev);
 	msleep(100);
-	flush_work(&dev->worker);
+	if (dev->worker.func)
+		flush_work(&dev->worker);
 	mutex_lock(&dev->io_mutex);
 	hdpvr_cancel_queue(dev);
 	mutex_unlock(&dev->io_mutex);
-- 
2.25.1