linux-kernel - [PATCH 3.2 020/152] [media] uvcvideo: Fix destruction order in uvc

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Message-ID: <lsq.1424137613.3761078@decadent.org.uk>
Date:	Tue, 17 Feb 2015 01:46:53 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Laurent Pinchart" <laurent.pinchart@...asonboard.com>,
	"Takashi Iwai" <tiwai@...e.de>,
	"Mauro Carvalho Chehab" <mchehab@....samsung.com>
Subject: [PATCH 3.2 020/152] [media] uvcvideo: Fix destruction order in
 uvc_delete()

3.2.67-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@...e.de>

commit 2228d80dd05a4fc5a410fde847677b8fb3eb23d7 upstream.

We've got a bug report at disconnecting a Webcam, where the kernel
spews warnings like below:
  WARNING: CPU: 0 PID: 8385 at ../fs/sysfs/group.c:219 sysfs_remove_group+0x87/0x90()
  sysfs group c0b2350c not found for kobject 'event3'
  CPU: 0 PID: 8385 Comm: queue2:src Not tainted 3.16.2-1.gdcee397-default #1
  Hardware name: ASUSTeK Computer INC. A7N8X-E/A7N8X-E, BIOS ASUS A7N8X-E Deluxe ACPI BIOS Rev 1013  11/12/2004
    c08d0705 ddc75cbc c0718c5b ddc75ccc c024b654 c08c6d44 ddc75ce8 000020c1
    c08d0705 000000db c03d1ec7 c03d1ec7 00000009 00000000 c0b2350c d62c9064
    ddc75cd4 c024b6a3 00000009 ddc75ccc c08c6d44 ddc75ce8 ddc75cfc c03d1ec7
  Call Trace:
    [<c0205ba6>] try_stack_unwind+0x156/0x170
    [<c02046f3>] dump_trace+0x53/0x180
    [<c0205c06>] show_trace_log_lvl+0x46/0x50
    [<c0204871>] show_stack_log_lvl+0x51/0xe0
    [<c0205c67>] show_stack+0x27/0x50
    [<c0718c5b>] dump_stack+0x3e/0x4e
    [<c024b654>] warn_slowpath_common+0x84/0xa0
    [<c024b6a3>] warn_slowpath_fmt+0x33/0x40
    [<c03d1ec7>] sysfs_remove_group+0x87/0x90
    [<c05a2c54>] device_del+0x34/0x180
    [<c05e3989>] evdev_disconnect+0x19/0x50
    [<c05e06fa>] __input_unregister_device+0x9a/0x140
    [<c05e0845>] input_unregister_device+0x45/0x80
    [<f854b1d6>] uvc_delete+0x26/0x110 [uvcvideo]
    [<f84d66f8>] v4l2_device_release+0x98/0xc0 [videodev]
    [<c05a25bb>] device_release+0x2b/0x90
    [<c04ad8bf>] kobject_cleanup+0x6f/0x1a0
    [<f84d5453>] v4l2_release+0x43/0x70 [videodev]
    [<c0372f31>] __fput+0xb1/0x1b0
    [<c02650c1>] task_work_run+0x91/0xb0
    [<c024d845>] do_exit+0x265/0x910
    [<c024df64>] do_group_exit+0x34/0xa0
    [<c025a76f>] get_signal_to_deliver+0x17f/0x590
    [<c0201b6a>] do_signal+0x3a/0x960
    [<c02024f7>] do_notify_resume+0x67/0x90
    [<c071ebb5>] work_notifysig+0x30/0x3b
    [<b7739e60>] 0xb7739e5f
   ---[ end trace b1e56095a485b631 ]---

The cause is that uvc_status_cleanup() is called after usb_put_*() in
uvc_delete().  usb_put_*() removes the sysfs parent and eventually
removes the children recursively, so the later device_del() can't find
its sysfs.  The fix is simply rearrange the call orders in
uvc_delete() so that the child is removed before the parent.

Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=897736
Reported-and-tested-by: Martin Pluskal <mpluskal@...e.com>

Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@....samsung.com>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/media/video/uvc/uvc_driver.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/media/video/uvc/uvc_driver.c
+++ b/drivers/media/video/uvc/uvc_driver.c
@@ -1597,12 +1597,12 @@ static void uvc_delete(struct uvc_device
 {
 	struct list_head *p, *n;
 
-	usb_put_intf(dev->intf);
-	usb_put_dev(dev->udev);
-
 	uvc_status_cleanup(dev);
 	uvc_ctrl_cleanup_device(dev);
 
+	usb_put_intf(dev->intf);
+	usb_put_dev(dev->udev);
+
 	if (dev->vdev.dev)
 		v4l2_device_unregister(&dev->vdev);
 #ifdef CONFIG_MEDIA_CONTROLLER

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