linux-kernel - Re: [PATCH][next] drm/gma500: fix null dereference of pointer fb before null check

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Date:   Thu, 19 Dec 2019 15:39:04 +0100
From:   Patrik Jakobsson <patrik.r.jakobsson@...il.com>
To:     Colin King <colin.king@...onical.com>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        kernel-janitors@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][next] drm/gma500: fix null dereference of pointer fb
 before null check

On Mon, Dec 16, 2019 at 5:21 PM Colin King <colin.king@...onical.com> wrote:
>
> From: Colin Ian King <colin.king@...onical.com>
>
> Pointer fb is being dereferenced when assigning dev before it
> is null checked.  Fix this by only dereferencing dev after the
> null check.

Applied to drm-misc-next

Thanks
Patrik

>
> Fixes: 6b7ce2c4161a ("drm/gma500: Remove struct psb_fbdev")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/gpu/drm/gma500/accel_2d.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/gma500/accel_2d.c b/drivers/gpu/drm/gma500/accel_2d.c
> index b9e5a38632f7..adc0507545bf 100644
> --- a/drivers/gpu/drm/gma500/accel_2d.c
> +++ b/drivers/gpu/drm/gma500/accel_2d.c
> @@ -228,8 +228,8 @@ static void psbfb_copyarea_accel(struct fb_info *info,
>  {
>         struct drm_fb_helper *fb_helper = info->par;
>         struct drm_framebuffer *fb = fb_helper->fb;
> -       struct drm_device *dev = fb->dev;
> -       struct drm_psb_private *dev_priv = dev->dev_private;
> +       struct drm_device *dev;
> +       struct drm_psb_private *dev_priv;
>         uint32_t offset;
>         uint32_t stride;
>         uint32_t src_format;
> @@ -238,6 +238,8 @@ static void psbfb_copyarea_accel(struct fb_info *info,
>         if (!fb)
>                 return;
>
> +       dev = fb->dev;
> +       dev_priv = dev->dev_private;
>         offset = to_gtt_range(fb->obj[0])->offset;
>         stride = fb->pitches[0];
>
> --
> 2.24.0
>