[PATCH] media: rockchip/rga: fix a use after free in rga_probe()

[PATCH] media: rockchip/rga: fix a use after free in rga_probe()

[Dan Carpenter]

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@oracle.com>
---
 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:
-- 
2.30.2

Re: [PATCH] media: rockchip/rga: fix a use after free in rga_probe()

[Dongliang Mu]

On Fri, Jul 9, 2021 at 2:38 PM Dan Carpenter <dan.carpenter@oracle.com> 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@oracle.com>
> ---
>  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:

        pm_runtime_enable(rga->dev);

        ret = v4l2_device_register(&pdev->dev, &rga->v4l2_dev);

        vfd = video_device_alloc();

        rga->m2m_dev = v4l2_m2m_init(&rga_m2m_ops);

        rga->cmdbuf_virt = dma_alloc_attrs(rga->dev, RGA_CMDBUF_SIZE,
                                           &rga->cmdbuf_phy, GFP_KERNEL,
                                           DMA_ATTR_WRITE_COMBINE);

        rga->src_mmu_pages =
                (unsigned int *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 3);
        rga->dst_mmu_pages =
                (unsigned int *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 3);

        ret = video_register_device(vfd, VFL_TYPE_VIDEO, -1);
        ......
        video_unregister_device(rga->vfd);

        free_pages((unsigned long)rga->src_mmu_pages, 3);
        free_pages((unsigned long)rga->dst_mmu_pages, 3);

        dma_free_attrs(rga->dev, RGA_CMDBUF_SIZE, rga->cmdbuf_virt,
                       rga->cmdbuf_phy, DMA_ATTR_WRITE_COMBINE);

        v4l2_m2m_release(rga->m2m_dev);

        video_device_release(rga->vfd);

        v4l2_device_unregister(&rga->v4l2_dev);

        pm_runtime_disable(rga->dev);

So I think the error handling code is more complex than this patch. ;(

> --
> 2.30.2
>

Re: [PATCH] media: rockchip/rga: fix a use after free in rga_probe()

[Dan Carpenter]

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@oracle.com> 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@oracle.com>
> > ---
> >  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