linux-kernel - Re: [PATCH] gma500: fix an incorrect NULL check on list iterator

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Date:   Tue, 29 Mar 2022 11:36:15 +0200
From:   Patrik Jakobsson <patrik.r.jakobsson@...il.com>
To:     Xiaomeng Tong <xiam0nd.tong@...il.com>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH] gma500: fix an incorrect NULL check on list iterator

On Sun, Mar 27, 2022 at 7:20 AM Xiaomeng Tong <xiam0nd.tong@...il.com> wrote:
>
> The bug is here:
>         return crtc;
>
> The list iterator value 'crtc' will *always* be set and non-NULL by
> list_for_each_entry(), so it is incorrect to assume that the iterator
> value will be NULL if the list is empty or no element is found.
>
> To fix the bug, return 'crtc' when found, otherwise return NULL.
>
> Cc: stable@...r.kernel.org
> fixes: 89c78134cc54d ("gma500: Add Poulsbo support")
> Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>

Thanks for the patch

Applied to drm-misc-next

-Patrik

> ---
>  drivers/gpu/drm/gma500/psb_intel_display.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/gma500/psb_intel_display.c b/drivers/gpu/drm/gma500/psb_intel_display.c
> index d5f95212934e..42d1a733e124 100644
> --- a/drivers/gpu/drm/gma500/psb_intel_display.c
> +++ b/drivers/gpu/drm/gma500/psb_intel_display.c
> @@ -535,14 +535,15 @@ void psb_intel_crtc_init(struct drm_device *dev, int pipe,
>
>  struct drm_crtc *psb_intel_get_crtc_from_pipe(struct drm_device *dev, int pipe)
>  {
> -       struct drm_crtc *crtc = NULL;
> +       struct drm_crtc *crtc;
>
>         list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
>                 struct gma_crtc *gma_crtc = to_gma_crtc(crtc);
> +
>                 if (gma_crtc->pipe == pipe)
> -                       break;
> +                       return crtc;
>         }
> -       return crtc;
> +       return NULL;
>  }
>
>  int gma_connector_clones(struct drm_device *dev, int type_mask)
> --
> 2.17.1
>