[libcamera-devel] [PATCH 02/15] v4l2: v4l2_camera_proxy: Check for null arg values in ioctl handlers

[Jacopo Mondi]

Hi Paul,

On Wed, Jun 17, 2020 at 06:30:31PM +0900, Paul Elder wrote:
> On Wed, Jun 17, 2020 at 04:06:07AM +0300, Laurent Pinchart wrote:
> > Hi Paul,
> >
> > Thank you for the patch.
> >
> > On Tue, Jun 16, 2020 at 10:12:31PM +0900, Paul Elder wrote:
> > > The ioctl handlers currently don't check if arg is null, so if it ever
> > > is, it will cause a segfault. Check that arg is null and return -EFAULT
> > > in all vidioc ioctl handlers.
> > >
> > > Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> >
> > Can't you check that in V4L2CameraProxy::ioctl() ?
>
> We can't do that. v4l2-compliance requires that 1) querycap shold not
> return EFAULT when arg == NULL, and 2) invalid ioctl should return

@@ -238,6 +238,9 @@ int V4L2CameraProxy::vidioc_querycap(struct v4l2_capability *arg)
 {
        LOG(V4L2Compat, Debug) << "Servicing vidioc_querycap";

+       if (arg == nullptr)
+               return -EFAULT;
+

Doesn't this return EFAUL on querycap with !arg ?

> ENOTTY. Because of the second point, we would still have to check at
> every ioctl.

You could work it around with a
bool is_ioctl_valid(unsigned long request)
{
        switch (request) {
        case VIDIOC_QUERYCAP:
        case VIDIOC_G_FMT:
        ....
                return true;
        default:
                return false;
        }
}

If you happen to have to check for an ioctl to be supported in
multiple places, otherwise I'm not sure it's worth it.

>
>
> Paul
>
>
> > > ---
> > >  src/v4l2/v4l2_camera_proxy.cpp | 33 +++++++++++++++++++++++++++++++--
> > >  1 file changed, 31 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> > > index 594dd13..5b74b53 100644
> > > --- a/src/v4l2/v4l2_camera_proxy.cpp
> > > +++ b/src/v4l2/v4l2_camera_proxy.cpp
> > > @@ -238,6 +238,9 @@ int V4L2CameraProxy::vidioc_querycap(struct v4l2_capability *arg)
> > >  {
> > >  	LOG(V4L2Compat, Debug) << "Servicing vidioc_querycap";
> > >
> > > +	if (arg == nullptr)
> > > +		return -EFAULT;
> > > +
> > >  	*arg = capabilities_;
> > >
> > >  	return 0;
> > > @@ -247,6 +250,8 @@ int V4L2CameraProxy::vidioc_enum_fmt(int fd, struct v4l2_fmtdesc *arg)
> > >  {
> > >  	LOG(V4L2Compat, Debug) << "Servicing vidioc_enum_fmt fd = " << fd;
> > >
> > > +	if (arg == nullptr)
> > > +		return -EFAULT;
> > >
> > >  	if (!validateBufferType(arg->type) ||
> > >  	    arg->index >= streamConfig_.formats().pixelformats().size())
> > > @@ -264,6 +269,8 @@ int V4L2CameraProxy::vidioc_g_fmt(int fd, struct v4l2_format *arg)
> > >  {
> > >  	LOG(V4L2Compat, Debug) << "Servicing vidioc_g_fmt fd = " << fd;
> > >
> > > +	if (arg == nullptr)
> > > +		return -EFAULT;
> > >
> > >  	if (!validateBufferType(arg->type))
> > >  		return -EINVAL;
> > > @@ -303,6 +310,9 @@ int V4L2CameraProxy::vidioc_s_fmt(int fd, struct v4l2_format *arg)
> > >  {
> > >  	LOG(V4L2Compat, Debug) << "Servicing vidioc_s_fmt fd = " << fd;
> > >
> > > +	if (arg == nullptr)
> > > +		return -EFAULT;
> > > +
> > >  	int ret = lock(fd);
> > >  	if (ret < 0)
> > >  		return ret;
> > > @@ -334,6 +344,9 @@ int V4L2CameraProxy::vidioc_try_fmt(int fd, struct v4l2_format *arg)
> > >  {
> > >  	LOG(V4L2Compat, Debug) << "Servicing vidioc_try_fmt fd = " << fd;
> > >
> > > +	if (arg == nullptr)
> > > +		return -EFAULT;
> > > +
> > >  	if (!validateBufferType(arg->type))
> > >  		return -EINVAL;
> > >
> > > @@ -361,6 +374,8 @@ int V4L2CameraProxy::vidioc_reqbufs(int fd, struct v4l2_requestbuffers *arg)
> > >  {
> > >  	LOG(V4L2Compat, Debug) << "Servicing vidioc_reqbufs fd = " << fd;
> > >
> > > +	if (arg == nullptr)
> > > +		return -EFAULT;
> > >
> > >  	int ret = lock(fd);
> > >  	if (ret < 0)
> > > @@ -444,6 +459,9 @@ int V4L2CameraProxy::vidioc_querybuf(int fd, struct v4l2_buffer *arg)
> > >  {
> > >  	LOG(V4L2Compat, Debug) << "Servicing vidioc_querybuf fd = " << fd;
> > >
> > > +	if (arg == nullptr)
> > > +		return -EFAULT;
> > > +
> > >  	int ret = lock(fd);
> > >  	if (ret < 0)
> > >  		return ret;
> > > @@ -461,8 +479,10 @@ int V4L2CameraProxy::vidioc_querybuf(int fd, struct v4l2_buffer *arg)
> > >
> > >  int V4L2CameraProxy::vidioc_qbuf(int fd, struct v4l2_buffer *arg)
> > >  {
> > > -	LOG(V4L2Compat, Debug) << "Servicing vidioc_qbuf, index = "
> > > -			       << arg->index << " fd = " << fd;
> > > +	LOG(V4L2Compat, Debug) << "Servicing vidioc_qbuf fd = " << fd;
> > > +
> > > +	if (arg == nullptr)
> > > +		return -EFAULT;
> > >
> > >  	int ret = lock(fd);
> > >  	if (ret < 0)
> > > @@ -487,6 +507,9 @@ int V4L2CameraProxy::vidioc_dqbuf(int fd, struct v4l2_buffer *arg)
> > >  {
> > >  	LOG(V4L2Compat, Debug) << "Servicing vidioc_dqbuf fd = " << fd;
> > >
> > > +	if (arg == nullptr)
> > > +		return -EFAULT;
> > > +
> > >  	int ret = lock(fd);
> > >  	if (ret < 0)
> > >  		return ret;
> > > @@ -522,6 +545,9 @@ int V4L2CameraProxy::vidioc_streamon(int fd, int *arg)
> > >  {
> > >  	LOG(V4L2Compat, Debug) << "Servicing vidioc_streamon fd = " << fd;
> > >
> > > +	if (arg == nullptr)
> > > +		return -EFAULT;
> > > +
> > >  	int ret = lock(fd);
> > >  	if (ret < 0)
> > >  		return ret;
> > > @@ -538,6 +564,9 @@ int V4L2CameraProxy::vidioc_streamoff(int fd, int *arg)
> > >  {
> > >  	LOG(V4L2Compat, Debug) << "Servicing vidioc_streamoff fd = " << fd;
> > >
> > > +	if (arg == nullptr)
> > > +		return -EFAULT;
> > > +
> > >  	int ret = lock(fd);
> > >  	if (ret < 0)
> > >  		return ret;
> >
> > --
> > Regards,
> >
> > Laurent Pinchart
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