Re: [PATCH] [Patch v2] usbtv: Fix refcounting mixup

[Oliver Neukum <oneukum@suse.de>]

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Am Mittwoch, den 16.05.2018, 12:27 +0200 schrieb Hans Verkuil:
> On 05/16/18 11:23, Oliver Neukum wrote:
> > Am Dienstag, den 15.05.2018, 18:01 +0200 schrieb Hans Verkuil:
> > > On 05/15/2018 05:46 PM, Oliver Neukum wrote:
> > > > Am Dienstag, den 15.05.2018, 16:28 +0200 schrieb Hans Verkuil:
> > > > > On 05/15/18 15:07, Oliver Neukum wrote:

> > Eh, but we cannot create a V4L device before the first device
> > is connected and we must certainly create multiple V4L devices if
> > multiple physical devices are connected.
> 
> v4l2_device_register is a terrible name. It does not create devices
> or register with anything, it just initializes a root data structure. I have
> proposed renaming this to v4l2_root_init() in the past, but people didn't
> want a big rename action.
> 
> BTW, with 'global data structure' I meant a data structure in struct usbtv.
> All I meant to say is that v4l2_device_register should be called in probe(),
> not in usbtv_video_init().

Hi,

Sorry for thread necromancy I am cleaning up electronically.
This patch has fallen through the cracks. As far as I can see the issue
is still open. I screwed this up. So do you want me to do a major
redesign? If not, what is to be done?

	Regards
		Oliver



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From c6040618651d670b895198096e3fa442b6cf8a26 Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@suse.com>
Date: Tue, 15 May 2018 12:16:26 +0200
Subject: [PATCH] [Patch v2] usbtv: Fix refcounting mixup

The premature free in the error path is blocked by V4L
refcounting, not USB refcounting. Thanks to
Ben Hutchings for review.

[v2] corrected attributions

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Fixes: 50e704453553 ("media: usbtv: prevent double free in error case")
CC: stable@vger.kernel.org
Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
---
 drivers/media/usb/usbtv/usbtv-core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/usbtv/usbtv-core.c b/drivers/media/usb/usbtv/usbtv-core.c
index ee9c656d121f..2308c0b4f5e7 100644
--- a/drivers/media/usb/usbtv/usbtv-core.c
+++ b/drivers/media/usb/usbtv/usbtv-core.c
@@ -113,7 +113,8 @@ static int usbtv_probe(struct usb_interface *intf,
 
 usbtv_audio_fail:
 	/* we must not free at this point */
-	usb_get_dev(usbtv->udev);
+	v4l2_device_get(&usbtv->v4l2_dev);
+	/* this will undo the v4l2_device_get() */
 	usbtv_video_free(usbtv);
 
 usbtv_video_fail:
-- 
2.16.4