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From:   Dongliang Mu <mudongliangabcd@gmail.com>
Date:   Fri, 9 Jul 2021 17:49:26 +0800
Message-ID: <CAD-N9QV-x3pzwN4HvpR9w04NnVHs1aafASQvD+gpTWg01K_YUw@mail.gmail.com>
Subject: Re: [PATCH] media: rockchip/rga: fix a use after free in rga_probe()
To:     Dan Carpenter <dan.carpenter@oracle.com>
Cc:     Jacob Chen <jacob-chen@iotwrt.com>,
        Ezequiel Garcia <ezequiel@collabora.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Heiko Stuebner <heiko@sntech.de>,
        Hans Verkuil <hansverk@cisco.com>, linux-media@vger.kernel.org,
        linux-rockchip@lists.infradead.org,
        linux-kernel <linux-kernel@vger.kernel.org>,
        kernel-janitors@vger.kernel.org
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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
>