Re: [PATCH v4 04/18] drm/panthor: Flush the cleanup_wq in the unplug path

[Liviu Dudau <liviu.dudau@arm.com>]

On Wed, Aug 26, 2026 at 04:56:03PM +0200, Boris Brezillon wrote:
> If we don't do that, we might face various UAFs, because the resource
> referenced by these work items might be gone by the time they get
> executed.
> 
> In each subcomponent making use of the panthor_cleanup_wq, we add a
> flush_workqueue() at the end of the _unplug() function. Note that this
> assumes no more work items from this subcomponent gets queued after
> that point, which is not yet guaranteed, but this will be fixed in
> upcoming changes.
> 
> Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block")
> Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
> Reported-by: sashiko-bot@kernel.org
> Closes: https://sashiko.dev/#/patchset/20260625-panthor-signal-from-irq-v5-0-8836a74e0ef9@collabora.com?part=2
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>

Best regards,
Liviu

> ---
>  drivers/gpu/drm/panthor/panthor_mmu.c   | 6 ++++++
>  drivers/gpu/drm/panthor/panthor_sched.c | 6 ++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index d43ba1c7cd2a..1385ee28bee5 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -3367,6 +3367,12 @@ void panthor_mmu_unplug(struct panthor_device *ptdev)
>  		}
>  	}
>  	mutex_unlock(&ptdev->mmu->as.slots_lock);
> +
> +	/* Ensure any pending job cleanup work are executed before returning,
> +	 * otherwise those might access objects that are gone if the work is
> +	 * executed after other components are unplugged.
> +	 */
> +	flush_workqueue(panthor_cleanup_wq);
>  }
>  
>  static void panthor_mmu_release_wq(struct drm_device *ddev, void *res)
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index 42adfc76b9e1..a6d57dc1b43e 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -4049,6 +4049,12 @@ void panthor_sched_unplug(struct panthor_device *ptdev)
>  		sched->pm.has_ref = false;
>  	}
>  	mutex_unlock(&sched->lock);
> +
> +	/* Ensure any pending group release work are executed before returning,
> +	 * otherwise those might access objects that are gone if the work is
> +	 * executed after other components are unplugged.
> +	 */
> +	flush_workqueue(panthor_cleanup_wq);
>  }
>  
>  static void panthor_sched_fini(struct drm_device *ddev, void *res)
> 
> -- 
> 2.55.0
> 

-- 
====================
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| but they're not |
| giving me the   |
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