drm/panthor: Reset the FW VM to NULL on unplug

bbrezillon · bbrezillon · commit a257e8182261 · 2024-05-13T09:52:19.000+02:00
This way get NULL derefs instead of use-after-free if the FW VM is referenced after the device has been unplugged. Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com> Reviewed-by: Steven Price <steven.price@arm.com> Acked-by: Liviu Dudau <liviu.dudau@arm.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240502183813.1612017-4-boris.brezillon@collabora.com
diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
@@ -1142,6 +1142,7 @@ void panthor_fw_unplug(struct panthor_device *ptdev)
 	 * state to keep the active_refcnt balanced.
 	 */
 	panthor_vm_put(ptdev->fw->vm);
+	ptdev->fw->vm = NULL;
 
 	panthor_gpu_power_off(ptdev, L2, ptdev->gpu_info.l2_present, 20000);
 }

Original file line number	Diff line number	Diff line change
`@@ -1142,6 +1142,7 @@ void panthor_fw_unplug(struct panthor_device *ptdev)`
`1142`	`1142`	`* state to keep the active_refcnt balanced.`
`1143`	`1143`	`*/`
`1144`	`1144`	`panthor_vm_put(ptdev->fw->vm);`
	`1145`	`+ ptdev->fw->vm = NULL;`
`1145`	`1146`
`1146`	`1147`	`panthor_gpu_power_off(ptdev, L2, ptdev->gpu_info.l2_present, 20000);`
`1147`	`1148`	`}`