Re: [PATCH 1/1] v4l: ioctl: Validate num_planes before using it

[Sakari Ailus <sakari.ailus@linux.intel.com>]

On Thu, Jan 10, 2019 at 03:11:35PM +0100, Hans Verkuil wrote:
> On 01/10/19 14:41, Sakari Ailus wrote:
> > On Thu, Jan 10, 2019 at 02:02:14PM +0100, Hans Verkuil wrote:
> >> On 01/10/19 13:43, Sakari Ailus wrote:
> >>> The for loop to reset the memory of the plane reserved fields runs over
> >>> num_planes provided by the user without validating it. Ensure num_planes
> >>> is no more than VIDEO_MAX_PLANES before the loop.
> >>>
> >>> Fixes: 4e1e0eb0e074 ("media: v4l2-ioctl: Zero v4l2_plane_pix_format reserved fields")
> >>> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> >>> ---
> >>> Hi folks,
> >>>
> >>> This patch goes on top of Thierry's patch "media: v4l2-ioctl: Clear only
> >>> per-plane reserved fields".
> >>>
> >>>  drivers/media/v4l2-core/v4l2-ioctl.c | 8 ++++++++
> >>>  1 file changed, 8 insertions(+)
> >>>
> >>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> >>> index 392f1228af7b5..9e68a608ac6d3 100644
> >>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> >>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> >>> @@ -1551,6 +1551,8 @@ static int v4l_s_fmt(const struct v4l2_ioctl_ops *ops,
> >>>  		if (unlikely(!ops->vidioc_s_fmt_vid_cap_mplane))
> >>>  			break;
> >>>  		CLEAR_AFTER_FIELD(p, fmt.pix_mp.xfer_func);
> >>> +		if (p->fmt.pix_mp.num_planes > VIDEO_MAX_PLANES)
> >>> +			break;
> >>
> >> I would check this not here but in check_fmt: all *_FMT ioctls call that function
> >> first, so it makes sense to do the check there.
> > 
> > Even G_FMT? I'm not saying no though. There's just a slight chance of
> > breaking something as it hasn't been a problem to call G_FMT with incorrect
> > number of planes in the mplane format; the number would be overwritten
> > anyway.
> 
> Not G_FMT since everything after the type field is zeroed.
> 
> > Apart from that, this leaves just the four locations --- putting this to a
> > separate function will reduce the calls to that function to just two.
> 
> I was a bit too quick with my comment about check_fmt. Your original patch
> is fine.
> 
> I'll Ack your patch.

Thanks. Could you pick this to your tree as you did Thierry's patch?

I'll submit the other patch in a moment.

> 
> Regards,
> 
> 	Hans
> 
> > 
> >>
> >> v4l_print_format should also be adjusted (take the minimum of num_planes and
> >> VIDEO_MAX_PLANES), since it can still be called even if check_fmt returns an
> >> error if num_planes is too large.
> >>
> >> In fact, the change to v4l_print_format should be a separate patch since that
> >> should be backported. It can leak memory in the kernel log if num_planes is
> >> too large.
> >>
> >> Regards,
> >>
> >> 	Hans
> >>
> >>>  		for (i = 0; i < p->fmt.pix_mp.num_planes; i++)
> >>>  			CLEAR_AFTER_FIELD(&p->fmt.pix_mp.plane_fmt[i], bytesperline);
> >>>  		return ops->vidioc_s_fmt_vid_cap_mplane(file, fh, arg);
> >>> @@ -1581,6 +1583,8 @@ static int v4l_s_fmt(const struct v4l2_ioctl_ops *ops,
> >>>  		if (unlikely(!ops->vidioc_s_fmt_vid_out_mplane))
> >>>  			break;
> >>>  		CLEAR_AFTER_FIELD(p, fmt.pix_mp.xfer_func);
> >>> +		if (p->fmt.pix_mp.num_planes > VIDEO_MAX_PLANES)
> >>> +			break;
> >>>  		for (i = 0; i < p->fmt.pix_mp.num_planes; i++)
> >>>  			CLEAR_AFTER_FIELD(&p->fmt.pix_mp.plane_fmt[i], bytesperline);
> >>>  		return ops->vidioc_s_fmt_vid_out_mplane(file, fh, arg);
> >>> @@ -1648,6 +1652,8 @@ static int v4l_try_fmt(const struct v4l2_ioctl_ops *ops,
> >>>  		if (unlikely(!ops->vidioc_try_fmt_vid_cap_mplane))
> >>>  			break;
> >>>  		CLEAR_AFTER_FIELD(p, fmt.pix_mp.xfer_func);
> >>> +		if (p->fmt.pix_mp.num_planes > VIDEO_MAX_PLANES)
> >>> +			break;
> >>>  		for (i = 0; i < p->fmt.pix_mp.num_planes; i++)
> >>>  			CLEAR_AFTER_FIELD(&p->fmt.pix_mp.plane_fmt[i], bytesperline);
> >>>  		return ops->vidioc_try_fmt_vid_cap_mplane(file, fh, arg);
> >>> @@ -1678,6 +1684,8 @@ static int v4l_try_fmt(const struct v4l2_ioctl_ops *ops,
> >>>  		if (unlikely(!ops->vidioc_try_fmt_vid_out_mplane))
> >>>  			break;
> >>>  		CLEAR_AFTER_FIELD(p, fmt.pix_mp.xfer_func);
> >>> +		if (p->fmt.pix_mp.num_planes > VIDEO_MAX_PLANES)
> >>> +			break;
> >>>  		for (i = 0; i < p->fmt.pix_mp.num_planes; i++)
> >>>  			CLEAR_AFTER_FIELD(&p->fmt.pix_mp.plane_fmt[i], bytesperline);
> >>>  		return ops->vidioc_try_fmt_vid_out_mplane(file, fh, arg);
> >>>
> >>
> > 
> 

-- 
Sakari Ailus
sakari.ailus@linux.intel.com