[PATCH] drm/gma500: fix null pointer dereference in psb_intel_lvds_get_modes

[PATCH] drm/gma500: fix null pointer dereference in psb_intel_lvds_get_modes

[Ma Ke]

In psb_intel_lvds_get_modes(), the return value of drm_mode_duplicate() is
assigned to mode, which will lead to a possible NULL pointer dereference
on failure of drm_mode_duplicate(). Add a check to avoid npd.

Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
 drivers/gpu/drm/gma500/psb_intel_lvds.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/gma500/psb_intel_lvds.c b/drivers/gpu/drm/gma500/psb_intel_lvds.c
index 8486de230ec9..aa5bf2a8a319 100644
--- a/drivers/gpu/drm/gma500/psb_intel_lvds.c
+++ b/drivers/gpu/drm/gma500/psb_intel_lvds.c
@@ -504,6 +504,8 @@ static int psb_intel_lvds_get_modes(struct drm_connector *connector)
 	if (mode_dev->panel_fixed_mode != NULL) {
 		struct drm_display_mode *mode =
 		    drm_mode_duplicate(dev, mode_dev->panel_fixed_mode);
+		if (!mode)
+			return -ENOMEM;
 		drm_mode_probed_add(connector, mode);
 		return 1;
 	}
-- 
2.25.1

Re: [PATCH] drm/gma500: fix null pointer dereference in psb_intel_lvds_get_modes

[Jani Nikula]

On Wed, 26 Jun 2024, Ma Ke <make24@iscas.ac.cn> wrote:
> In psb_intel_lvds_get_modes(), the return value of drm_mode_duplicate() is
> assigned to mode, which will lead to a possible NULL pointer dereference
> on failure of drm_mode_duplicate(). Add a check to avoid npd.
>
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>
> ---
>  drivers/gpu/drm/gma500/psb_intel_lvds.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/gma500/psb_intel_lvds.c b/drivers/gpu/drm/gma500/psb_intel_lvds.c
> index 8486de230ec9..aa5bf2a8a319 100644
> --- a/drivers/gpu/drm/gma500/psb_intel_lvds.c
> +++ b/drivers/gpu/drm/gma500/psb_intel_lvds.c
> @@ -504,6 +504,8 @@ static int psb_intel_lvds_get_modes(struct drm_connector *connector)
>  	if (mode_dev->panel_fixed_mode != NULL) {
>  		struct drm_display_mode *mode =
>  		    drm_mode_duplicate(dev, mode_dev->panel_fixed_mode);
> +		if (!mode)
> +			return -ENOMEM;

Do not return negative values from .get_modes().

BR,
Jani.

>  		drm_mode_probed_add(connector, mode);
>  		return 1;
>  	}

-- 
Jani Nikula, Intel

Re: [PATCH] drm/gma500: fix null pointer dereference in psb_intel_lvds_get_modes

[Markus Elfring]

> In psb_intel_lvds_get_modes(), the return value of drm_mode_duplicate() is
> assigned to mode, which will lead to a possible NULL pointer dereference
> on failure of drm_mode_duplicate(). Add a check to avoid npd.

1. Can a wording approach (like the following) be a better change description?

   A null pointer is stored in the local variable “mode” after a call
   of the function “drm_mode_duplicate” failed. This pointer was passed to
   a subsequent call of the function “drm_mode_probed_add” where an undesirable
   dereference will be performed then.
   Thus add a corresponding return value check.


2. Would you like to add any tags (like “Fixes” and “Cc”) accordingly?


3. How do you think about to append parentheses to the function name
   in the summary phrase?


4. How do you think about to put similar results from static source code
   analyses into corresponding patch series?


Regards,
Markus