On Tue, Jan 25, 2022 at 01:16:18AM +0800, Zhou Qingyang wrote:
> In cx23885_video_register(), the return value of cx23885_vdev_init() is
> assigned to dev->video_dev and there is a dereference of it after that.
> the return value of cx23885_vdev_init() could be NULL on failure of
> allocation, which could lead to a NULL pointer dereference.
>
> the same as dev->vbi_dev.
>
> Fix this bug by adding a NULL check of dev->video_dev and dev->vbi_dev.
>
> This bug was found by a static analyzer.
>
> Builds with 'make allyesconfig' show no new warnings,
> and our static analyzer no longer warns about this code.
>
> Fixes: 453afdd9ce33 ("[media] cx23885: convert to vb2")
> Signed-off-by: Zhou Qingyang <zhou1615@xxxxxxx>
> ---
> The analysis employs differential checking to identify inconsistent
> security operations (e.g., checks or kfrees) between two code paths
> and confirms that the inconsistent operations are not recovered in the
> current function or the callers, so they constitute bugs.
>
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
>
> drivers/media/pci/cx23885/cx23885-video.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/media/pci/cx23885/cx23885-video.c b/drivers/media/pci/cx23885/cx23885-video.c
> index a380e0920a21..1b95109eff8c 100644
> --- a/drivers/media/pci/cx23885/cx23885-video.c
> +++ b/drivers/media/pci/cx23885/cx23885-video.c
> @@ -1353,6 +1353,11 @@ int cx23885_video_register(struct cx23885_dev *dev)
> /* register Video device */
> dev->video_dev = cx23885_vdev_init(dev, dev->pci,
> &cx23885_video_template, "video");
> + if (!dev->video_dev) {
> + err = -ENOMEM;
> + goto fail_unreg;
> + }
> +
> dev->video_dev->queue = &dev->vb2_vidq;
> dev->video_dev->device_caps = V4L2_CAP_READWRITE | V4L2_CAP_STREAMING |
> V4L2_CAP_AUDIO | V4L2_CAP_VIDEO_CAPTURE;
> @@ -1381,6 +1386,11 @@ int cx23885_video_register(struct cx23885_dev *dev)
> /* register VBI device */
> dev->vbi_dev = cx23885_vdev_init(dev, dev->pci,
> &cx23885_vbi_template, "vbi");
> + if (!dev->vbi_dev) {
> + err = -ENOMEM;
> + goto fail_unreg;
> + }
> +
> dev->vbi_dev->queue = &dev->vb2_vbiq;
> dev->vbi_dev->device_caps = V4L2_CAP_READWRITE | V4L2_CAP_STREAMING |
> V4L2_CAP_AUDIO | V4L2_CAP_VBI_CAPTURE;
> --
> 2.25.1
>
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