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SubjectRe: [PATCH] [media] saa7146: fix a possible NULL pointer reference in saa7146_set_position
On Sun, Jan 05, 2014 at 10:08:00AM +0800, Ethan Zhao wrote:
> Function saa7146_format_by_fourcc() may return NULL, reference of the returned
> result would cause NULL pointer issue without checking.
>
> Signed-off-by: Ethan Zhao <ethan.kernel@gmail.com>
> ---
> drivers/media/common/saa7146/saa7146_hlp.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/common/saa7146/saa7146_hlp.c b/drivers/media/common/saa7146/saa7146_hlp.c
> index be746d1..3e23eab 100644
> --- a/drivers/media/common/saa7146/saa7146_hlp.c
> +++ b/drivers/media/common/saa7146/saa7146_hlp.c
> @@ -575,6 +575,7 @@ static void saa7146_set_position(struct saa7146_dev *dev, int w_x, int w_y, int
> */
> u32 base = (u32)(unsigned long)vv->ov_fb.base;
>
> + int which = 1;
> struct saa7146_video_dma vdma1;
>
> /* calculate memory offsets for picture, look if we shall top-down-flip */
> @@ -608,10 +609,14 @@ static void saa7146_set_position(struct saa7146_dev *dev, int w_x, int w_y, int
> vdma1.pitch *= -1;
> }
>
> - vdma1.base_page = sfmt->swap;
> + if (sfmt)
> + vdma1.base_page = sfmt->swap;
> + else
> + which = 0;
> +
> vdma1.num_line_byte = (vv->standard->v_field<<16)+vv->standard->h_pixels;
>
> - saa7146_write_out_dma(dev, 1, &vdma1);
> + saa7146_write_out_dma(dev, which, &vdma1);

If saa7146_format_by_fourcc() returns NULL you'll crash much earlier
when trying to do

int depth = sfmt->depth;

I am not familiar with the code by it seems you are papering over the
problem. Will we ever get here with unknown pixel format?

Thanks.

--
Dmitry


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