[PATCH v3] drm/imagination: Fix parameter validation in pvr_fw_object_destroy()

[PATCH v3] drm/imagination: Fix parameter validation in pvr_fw_object_destroy()

[Alexandru Dadu]

Fix parameter validation to avoid possible NULL pointer dereference from
pvr_fw_object_destroy() when handling allocation failures.

Sashiko report:
If pvr_gem_object_create() fails in
pvr_fw_object_create_and_map_common(), fw_obj->gem is explicitly set to
NULL before jumping to the error cleanup path.
The cleanup path then calls pvr_fw_object_destroy().

Reported-by: Sashiko <sashiko-bot@kernel.org>
Link: https://lore.kernel.org/dri-devel/20260810132202.3C16D1F000E9@smtp.kernel.org/
Fixes: cc1aeedb98ad ("drm/imagination: Implement firmware infrastructure and META FW support")
Signed-off-by: Alexandru Dadu <alexandru.dadu@imgtec.com>
---
Changes in v3:
- Skimed the commit message removing redundant information.
- Refactored the parameter validation to return early.
- Link to v2: https://patch.msgid.link/20260903-fix-null-pointer-dereference-v2-1-138ff9b6f805@imgtec.com

Changes in v2:
- Commit message and cover letter updates.
- Link to v1: https://patch.msgid.link/20260812-fix-null-pointer-dereference-v1-1-f69b2ffe9520@imgtec.com

To: Alessio Belle <alessio.belle@imgtec.com>
To: Luigi Santivetti <luigi.santivetti@imgtec.com>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
To: Maxime Ripard <mripard@kernel.org>
To: Thomas Zimmermann <tzimmermann@suse.de>
To: David Airlie <airlied@gmail.com>
To: Simona Vetter <simona@ffwll.ch>
To: Donald Robson <donald.robson@imgtec.com>
To: Sarah Walker <sarah.walker@imgtec.com>
Cc: imagination@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org
---
 drivers/gpu/drm/imagination/pvr_fw.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/imagination/pvr_fw.c b/drivers/gpu/drm/imagination/pvr_fw.c
index 850a3ec8e775..9977f4da3d8d 100644
--- a/drivers/gpu/drm/imagination/pvr_fw.c
+++ b/drivers/gpu/drm/imagination/pvr_fw.c
@@ -1429,6 +1429,12 @@ void pvr_fw_object_destroy(struct pvr_fw_object *fw_obj)
 	struct drm_gem_object *gem_obj = gem_from_pvr_gem(pvr_obj);
 	struct pvr_device *pvr_dev = to_pvr_device(gem_obj->dev);
 
+	if (!fw_obj)
+		return;
+
+	if (!fw_obj->gem)
+		return;
+
 	mutex_lock(&pvr_dev->fw_dev.fw_objs.lock);
 	list_del(&fw_obj->node);
 	mutex_unlock(&pvr_dev->fw_dev.fw_objs.lock);
@@ -1439,8 +1445,7 @@ void pvr_fw_object_destroy(struct pvr_fw_object *fw_obj)
 			return;
 	}
 
-	if (fw_obj->gem)
-		pvr_gem_object_put(fw_obj->gem);
+	pvr_gem_object_put(fw_obj->gem);
 
 	kfree(fw_obj);
 }

---
base-commit: bd4f284df04d76fd65e57141cb1e6e7a49e4c3cb
change-id: 20260812-fix-null-pointer-dereference-2c891142d988

Best regards,
--  
Alexandru Dadu <alexandru.dadu@imgtec.com>

Re: [PATCH v3] drm/imagination: Fix parameter validation in pvr_fw_object_destroy()

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] drm/imagination: memory leak of fw_obj on allocation error path
--

commit f0dd8a6ab034ccbc4cdc49ac4cbb537593b10a6d
Author: Alexandru Dadu <alexandru.dadu@imgtec.com>
Subject: drm/imagination: Fix parameter validation in pvr_fw_object_destroy()

This patch attempts to fix a possible NULL pointer dereference in
pvr_fw_object_destroy() when handling allocation failures in
pvr_fw_object_create_and_map_common() by returning early.

Link: https://lore.kernel.org/dri-devel/20260810132202.3C16D1F000E9@smtp.kernel.org/

> diff --git a/drivers/gpu/drm/imagination/pvr_fw.c b/drivers/gpu/drm/imagination/pvr_fw.c
> index 850a3ec8e7750..9977f4da3d8d7 100644
> --- a/drivers/gpu/drm/imagination/pvr_fw.c
> +++ b/drivers/gpu/drm/imagination/pvr_fw.c
> @@ -1429,6 +1429,12 @@ void pvr_fw_object_destroy(struct pvr_fw_object *fw_obj)
>  	struct drm_gem_object *gem_obj = gem_from_pvr_gem(pvr_obj);
>  	struct pvr_device *pvr_dev = to_pvr_device(gem_obj->dev);
>  
> +	if (!fw_obj)
> +		return;
> +
> +	if (!fw_obj->gem)
> +		return;

[Severity: High]
Does this code leave the original NULL pointer dereference unfixed?

Since the local variables gem_obj and pvr_dev are declared and initialized
before these new early returns, fw_obj and fw_obj->gem are implicitly
dereferenced by accessing gem_obj->dev before the check is ever reached.
If either is NULL, an oops will still occur at the start of the function.

[ ... ]

> @@ -1439,8 +1445,7 @@ void pvr_fw_object_destroy(struct pvr_fw_object *fw_obj)
>  			return;
>  	}
>  
> -	if (fw_obj->gem)
> -		pvr_gem_object_put(fw_obj->gem);
> +	pvr_gem_object_put(fw_obj->gem);
>  
>  	kfree(fw_obj);

[Severity: High]
Could the early return added above cause a memory leak regression?

In pvr_fw_object_create_and_map_common(), if pvr_gem_object_create() fails,
fw_obj->gem is set to NULL and the error cleanup path calls
pvr_fw_object_destroy().

The new early return for !fw_obj->gem skips this kfree(fw_obj) at the end of
the function, permanently leaking the firmware object structure.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260922-fix-null-pointer-dereference-v3-1-f099763ed676@imgtec.com?part=1