linux-kernel - Re: [syzbot] [usb?] [media?] possible deadlock in vb2_video_unregister

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Message-Id: <20240207110756.936-1-hdanton@sina.com>
Date: Wed,  7 Feb 2024 19:07:56 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+3b1d4b3d5f7a358bf9a9@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [usb?] [media?] possible deadlock in vb2_video_unregister_device

On Wed, 07 Feb 2024 00:44:22 -0800
> HEAD commit:    ed5551279c91 Merge 6.8-rc3 into usb-next
> git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1603629fe80000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git  usb-testing

--- x/drivers/media/usb/usbtv/usbtv-video.c
+++ y/drivers/media/usb/usbtv/usbtv-video.c
@@ -963,11 +963,11 @@ ctrl_fail:
 
 void usbtv_video_free(struct usbtv *usbtv)
 {
+	usbtv_stop(usbtv);
+	vb2_video_unregister_device(&usbtv->vdev);
 	mutex_lock(&usbtv->vb2q_lock);
 	mutex_lock(&usbtv->v4l2_lock);
 
-	usbtv_stop(usbtv);
-	vb2_video_unregister_device(&usbtv->vdev);
 	v4l2_device_disconnect(&usbtv->v4l2_dev);
 
 	mutex_unlock(&usbtv->v4l2_lock);
--