Re: [PATCH] vcodec: mediatek: add check for NULL for vsi->frm_bufs[vsi->new_fb_idx].buf.fb in vp9_swap_frm_bufs

[Nicolas Dufresne]

Hi,

Le vendredi 28 octobre 2022 à 15:58 +0300, Anastasia Belova a écrit :
> If vsi->frm_bufs[vsi->new_fb_idx].buf.fb == NULL while cleaning
> fb_free_list NULL-pointer is dereferenced.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: f77e89854b3e ("[media] vcodec: mediatek: Add Mediatek VP9 Video Decoder Driver")
> 
> Signed-off-by: Anastasia Belova <abelova@xxxxxxxxxxxxx>
> ---
>  drivers/media/platform/mediatek/vcodec/vdec/vdec_vp9_if.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/mediatek/vcodec/vdec/vdec_vp9_if.c b/drivers/media/platform/mediatek/vcodec/vdec/vdec_vp9_if.c
> index 70b8383f7c8e..b0679aaf6192 100644
> --- a/drivers/media/platform/mediatek/vcodec/vdec/vdec_vp9_if.c
> +++ b/drivers/media/platform/mediatek/vcodec/vdec/vdec_vp9_if.c
> @@ -512,7 +512,7 @@ static void vp9_swap_frm_bufs(struct vdec_vp9_inst *inst)
>  	 * clean fb_free_list
>  	 */
>  	if (vsi->frm_bufs[vsi->new_fb_idx].ref_cnt == 0) {
> -		if (!vp9_is_sf_ref_fb(
> +		if (vsi->frm_bufs[vsi->new_fb_idx].buf.fb != NULL && !vp9_is_sf_ref_fb(
>  			inst, vsi->frm_bufs[vsi->new_fb_idx].buf.fb)) {
>  			struct vdec_fb *fb;

Perhaps we could try and maintain some readability ? I'd suggest to move the
check into vp9_is_sf_ref_fb() as an early return.

Nicolas