2024-04-03 01:54:04

by Huai-Yuan Liu

Subject: [PATCH] drm/arm/malidp: fix a possible null pointer dereference

In malidp_mw_connector_reset, new memory is allocated with kzalloc, but
no check is performed. In order to prevent null pointer dereferencing,
ensure that mw_state is checked before calling
__drm_atomic_helper_connector_reset.

Fixes: 8cbc5caf36ef ("drm: mali-dp: Add writeback connector")
Signed-off-by: Huai-Yuan Liu <[email protected]>
---
drivers/gpu/drm/arm/malidp_mw.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/arm/malidp_mw.c b/drivers/gpu/drm/arm/malidp_mw.c
index 626709bec6f5..25623ef9be80 100644
--- a/drivers/gpu/drm/arm/malidp_mw.c
+++ b/drivers/gpu/drm/arm/malidp_mw.c
@@ -72,7 +72,9 @@ static void malidp_mw_connector_reset(struct drm_connector *connector)
__drm_atomic_helper_connector_destroy_state(connector->state);

kfree(connector->state);
- __drm_atomic_helper_connector_reset(connector, &mw_state->base);
+
+ if (mw_state)
+ __drm_atomic_helper_connector_reset(connector, &mw_state->base);
}

static enum drm_connector_status
--
2.34.1

2024-04-03 12:13:28

by Liviu Dudau

Subject: Re: [PATCH] drm/arm/malidp: fix a possible null pointer dereference

Hi,

On Wed, Apr 03, 2024 at 09:43:01AM +0800, Huai-Yuan Liu wrote:
>
> In malidp_mw_connector_reset, new memory is allocated with kzalloc, but
> no check is performed. In order to prevent null pointer dereferencing,
> ensure that mw_state is checked before calling
> __drm_atomic_helper_connector_reset.

Thanks for the patch, it does look like an oversight. Can I suggest you
respin your patch and add a

connector->state = NULL;

right after kfree(connector->state) ?

That way we can be sure we're not leaving state pointing to freed memory.

Best regards,
Liviu

>
> Fixes: 8cbc5caf36ef ("drm: mali-dp: Add writeback connector")
> Signed-off-by: Huai-Yuan Liu <[email protected]>
> ---
> drivers/gpu/drm/arm/malidp_mw.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/arm/malidp_mw.c b/drivers/gpu/drm/arm/malidp_mw.c
> index 626709bec6f5..25623ef9be80 100644
> --- a/drivers/gpu/drm/arm/malidp_mw.c
> +++ b/drivers/gpu/drm/arm/malidp_mw.c
> @@ -72,7 +72,9 @@ static void malidp_mw_connector_reset(struct drm_connector *connector)
> __drm_atomic_helper_connector_destroy_state(connector->state);
>
> kfree(connector->state);
> - __drm_atomic_helper_connector_reset(connector, &mw_state->base);
> +
> + if (mw_state)
> + __drm_atomic_helper_connector_reset(connector, &mw_state->base);
> }
>
> static enum drm_connector_status
> --
> 2.34.1
>

--
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