Date:   Sat, 29 Jun 2019 05:28:17 +0200
From:   Niklas Söderlund <niklas.soderlund@...n.se>
To:     Janusz Krzysztofik <jmkrzyszt@...il.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 0/3] media: v4l2-subdev: Verify arguments in
 v4l2_subdev_call()

Hi,

This patch breaks rcar-vin. I'm sorry I did not find out before it was 
merged as a8fa55078a7784a9 ("media: v4l2-subdev: Verify arguments in 
v4l2_subdev_call()").

The problem is that rcar-vin calls enum_mbus_code in its bound callback.  
At this point call_enum_mbus_code() is invoked which then calls 
check_pad(). At this point sd->entity.graph_obj.mdev is not set so the 
check if (pad > 0) fails and the binding of the subdevice in rcar-vin 
fails.

I'm not sure how to best solve this, suggestions are appreciated. I see 
two options, move the call to enum_mbus_code from the bound to the 
complete callback or make sure the mdev is associated with the subdev 
before the bound callback is invoked. I don't like the former as I think 
the complete callback should be removed ;-)

On 2019-05-20 23:27:44 +0200, Janusz Krzysztofik wrote:
> Correctness of format type (try or active) and pad ID parameters passed
> to subdevice operation callbacks is now verified only for IOCTL calls.
> However, those callbacks are also used by drivers, e.g., V4L2 host
> interfaces.
> 
> Since both subdev_do_ioctl() and drivers are using v4l2_subdev_call()
> macro while calling subdevice operations, move those parameter checks
> from subdev_do_ioctl() to v4l2_subdev_call().  Also, add check for
> non-NULL pointers, including pad config if V4L2_SUBDEV_FORMAT_TRY is
> requested.
> 
> Having that done, we can avoid taking care of those checks inside
> drivers.
> 
> Janusz Krzysztofik (3):
>   media: v4l2-subdev: Verify arguments in v4l2_subdev_call()
>   media: v4l2-subdev: Verify v4l2_subdev_call() pointer arguments
>   media: v4l2-subdev: Verify v4l2_subdev_call() pad config argument
> 
>  drivers/media/v4l2-core/v4l2-subdev.c | 268 +++++++++++++++++---------
>  include/media/v4l2-subdev.h           |   6 +
>  2 files changed, 188 insertions(+), 86 deletions(-)
> 
> Changelog:
> v6->v7:
> Changes suggested by Sakari - thanks!
> - never succeed pad check on media entities with pad_num == 0,
> - allow pad 0 on subdevies not registered as media entities.
> 
> v5->v6:
> - rename wrappers to call_something() as suggested by Sakari - thanks!
> - make check_ functions inline - also on Sakari's suggestion, thanks!
> - drop patch 2/4 and remove WARN_ONs from remaining patches to avoid
>   kernel WARNs on non-kernel bugs - thanks Hans for pointing this out!
> 
> v4->v5:
> - a few coding style and code formatting changes,
> - require CONFIG_MEDIA_CONTROLLER, not CONFIG_VIDEO_V4L2_SUBDEV_API,
>   for a valid pad ID check,
> - perform pad ID check only if at least one pad is configured so
>   drivers which don't configure pads are not affected if built with
>   CONFIG_MEDIA_CONTROLLER defined,
> - issue kernel warnings on invalid parameters (new patch - 2/4),
> - validate pointers before using them (new patch - 3/4).
> 
> v3->v4:
> - fix 'struct' keyword missing from patch 2/2,
> - fix checkpatch reported style issue in patch 2/2
> Sorry for that.
> 
> v2->v3:
> - add patch 2/2 with pad config check,
> - adjust continuation line alignments in patch 1/2 to match those
>   used in 2/2.
> 
> v1->v2:
> - replace the horrible macro with a structure of wrapper functions;
>   inspired by Hans' and Sakari's comments - thanks!
> 
> -- 
> 2.21.0
> 

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