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SubjectRe: [PATCH] media: qcom: venus: Fix a possible null-pointer dereference in vdec_g_fmt()
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This patch fell between the cracks, but while cleaning up patchwork
it popped up again :-)

On 7/27/19 11:15 AM, Jia-Ju Bai wrote:
> In vdec_g_fmt(), fmt is firstly assigned NULL, and it could be never
> assigned before being used on line 223:
> pixmp->pixelformat = fmt->pixfmt;
>
> Thus, a possible null-pointer dereference may occur.
>
> To fix this bug, fmt is checked before being used here.

Actually, this function can only be called for f->type values
V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE or V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE.

The easiest way to fix this is to replace this:

if (f->type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE)
fmt = inst->fmt_cap;
else if (f->type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE)
fmt = inst->fmt_out;

by:

if (f->type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE)
fmt = inst->fmt_cap;
else
fmt = inst->fmt_out;

And the same in a bit lower down in this function.

Regards,

Hans

>
> This bug is found by a static analysis tool STCheck written by us.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> ---
> drivers/media/platform/qcom/venus/vdec.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/platform/qcom/venus/vdec.c b/drivers/media/platform/qcom/venus/vdec.c
> index e1f998656c07..12c31551f191 100644
> --- a/drivers/media/platform/qcom/venus/vdec.c
> +++ b/drivers/media/platform/qcom/venus/vdec.c
> @@ -211,7 +211,8 @@ static int vdec_g_fmt(struct file *file, void *fh, struct v4l2_format *f)
> inst->height = format.fmt.pix_mp.height;
> }
>
> - pixmp->pixelformat = fmt->pixfmt;
> + if (fmt)
> + pixmp->pixelformat = fmt->pixfmt;
>
> if (f->type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE) {
> pixmp->width = inst->width;
>

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