[PATCH] gma500: fix an incorrect NULL check on list iterator

[PATCH] gma500: fix an incorrect NULL check on list iterator

[Xiaomeng Tong]

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@vger.kernel.org
fixes: 89c78134cc54d ("gma500: Add Poulsbo support")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
---
 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

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

[Patrik Jakobsson]

On Sun, Mar 27, 2022 at 7:20 AM Xiaomeng Tong <xiam0nd.tong@gmail.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@vger.kernel.org
> fixes: 89c78134cc54d ("gma500: Add Poulsbo support")
> Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.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
>