On Fri, Jul 09, 2021 at 05:49:26PM +0800, Dongliang Mu wrote:
> On Fri, Jul 9, 2021 at 2:38 PM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> >
> > The video_device_release() frees the "vfd" pointer so passing it to
> > video_unregister_device() on the next line results in a use after free.
> > Calling video_unregister_device() on a device that hasn't been
> > registered is supposed to be a no-op so that can be removed. The paths
> > with to goto unreg_video_dev have a memory leak and should be updated to
> > goto rel_vdev instead.
> >
> > Fixes: f7e7b48e6d79 ("[media] rockchip/rga: v4l2 m2m support")
> > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > ---
> > drivers/media/platform/rockchip/rga/rga.c | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/media/platform/rockchip/rga/rga.c b/drivers/media/platform/rockchip/rga/rga.c
> > index bf3fd71ec3af..37f7fd060c38 100644
> > --- a/drivers/media/platform/rockchip/rga/rga.c
> > +++ b/drivers/media/platform/rockchip/rga/rga.c
> > @@ -863,12 +863,12 @@ static int rga_probe(struct platform_device *pdev)
> > if (IS_ERR(rga->m2m_dev)) {
> > v4l2_err(&rga->v4l2_dev, "Failed to init mem2mem device\n");
> > ret = PTR_ERR(rga->m2m_dev);
> > - goto unreg_video_dev;
> > + goto rel_vdev;
> > }
> >
> > ret = pm_runtime_resume_and_get(rga->dev);
> > if (ret < 0)
> > - goto unreg_video_dev;
> > + goto rel_vdev;
> >
> > rga->version.major = (rga_read(rga, RGA_VERSION_INFO) >> 24) & 0xFF;
> > rga->version.minor = (rga_read(rga, RGA_VERSION_INFO) >> 20) & 0x0F;
> > @@ -904,8 +904,6 @@ static int rga_probe(struct platform_device *pdev)
> >
> > rel_vdev:
> > video_device_release(vfd);
> > -unreg_video_dev:
> > - video_unregister_device(rga->vfd);
> > unreg_v4l2_dev:
> > v4l2_device_unregister(&rga->v4l2_dev);
> > err_put_clk:
>
> >From the analysis of rga_probe and rga_remove function, the init and
> cleanup functions are in pairs as follows:
>
Yeah. You're right. It's leaky. This is like the stuff Christophe
Jaillet has been working on.
This is also slightly complicated because what about if the call to
device_register() fails inside video_register_device()? In that case
we're not allowed to call video_device_release(). I think the way
people deal with that is because device_register() never fails in real
life so let's ignore that possibility.
I sort of hate device_register() because it introduces a lot of bugs
like this which don't affect real life. Inside the __video_register_device()
function itself we just ignore errors from video_register_media_controller()
because there is no possible way to handle it in a bug free way. Again,
it's not a bug which is going to affect real life, but it's just
frustrating to not be able to write code which is correct in a technical
sense.
Ah well... Fine. I'll resend.
regards,
dan carpenter
