linux-kernel - Re: [PATCH v2 1/2] vb2: core: Skip planes array verification if pb is NULL

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Date:	Fri, 13 May 2016 11:09:19 +0200
From:	Hans Verkuil <hverkuil@...all.nl>
To:	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	linux-media@...r.kernel.org
Cc:	mchehab@....samsung.com, david@...olicited.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] vb2: core: Skip planes array verification if pb is
 NULL

On 05/12/2016 02:14 PM, Sakari Ailus wrote:
> An earlier patch fixing an input validation issue introduced another
> issue: vb2_core_dqbuf() is called with pb argument value NULL in some
> cases, causing a NULL pointer dereference. Fix this by skipping the
> verification as there's nothing to verify.
> 
> Signed-off-by: David R <david@...olicited.net>
> 
> Use if () instead of ? :; it's nicer that way. Improve the comment in the
> code as well.

This comment doesn't seem applicable to this patch.

Reviewed-by: Hans Verkuil <hans.verkuil@...co.com>

	Hans

> 
> Fixes: e7e0c3e26587 ("[media] videobuf2-core: Check user space planes array in dqbuf")
> 
> Signed-off-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> Cc: stable@...r.kernel.org # for v4.4 and later
> ---
>  drivers/media/v4l2-core/videobuf2-core.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
> index 9fbcb67..633fc1a 100644
> --- a/drivers/media/v4l2-core/videobuf2-core.c
> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> @@ -1648,7 +1648,7 @@ static int __vb2_get_done_vb(struct vb2_queue *q, struct vb2_buffer **vb,
>  			     void *pb, int nonblocking)
>  {
>  	unsigned long flags;
> -	int ret;
> +	int ret = 0;
>  
>  	/*
>  	 * Wait for at least one buffer to become available on the done_list.
> @@ -1664,10 +1664,12 @@ static int __vb2_get_done_vb(struct vb2_queue *q, struct vb2_buffer **vb,
>  	spin_lock_irqsave(&q->done_lock, flags);
>  	*vb = list_first_entry(&q->done_list, struct vb2_buffer, done_entry);
>  	/*
> -	 * Only remove the buffer from done_list if v4l2_buffer can handle all
> -	 * the planes.
> +	 * Only remove the buffer from done_list if all planes can be
> +	 * handled. Some cases such as V4L2 file I/O and DVB have pb
> +	 * == NULL; skip the check then as there's nothing to verify.
>  	 */
> -	ret = call_bufop(q, verify_planes_array, *vb, pb);
> +	if (pb)
> +		ret = call_bufop(q, verify_planes_array, *vb, pb);
>  	if (!ret)
>  		list_del(&(*vb)->done_entry);
>  	spin_unlock_irqrestore(&q->done_lock, flags);
>