Re: [Intel-gfx] [PATCH 1/2] drm/i915: Fix a potential UAF at device unload

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 08/09/2022 21:07, Nirmoy Das wrote:
> i915_gem_drain_freed_objects() might not be enough to
> free all the objects and RCU delayed work might get
> scheduled after the i915 device struct gets freed.
> 
> Call i915_gem_drain_workqueue() to catch all RCU delayed work.
> 
> Suggested-by: Chris Wilson <chris.p.wilson@intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 0f49ec9d494a..e8a053eaaa89 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1254,7 +1254,7 @@ void i915_gem_init_early(struct drm_i915_private *dev_priv)
>   
>   void i915_gem_cleanup_early(struct drm_i915_private *dev_priv)
>   {
> -	i915_gem_drain_freed_objects(dev_priv);
> +	i915_gem_drain_workqueue(dev_priv);
>   	GEM_BUG_ON(!llist_empty(&dev_priv->mm.free_list));
>   	GEM_BUG_ON(atomic_read(&dev_priv->mm.free_count));
>   	drm_WARN_ON(&dev_priv->drm, dev_priv->mm.shrink_count);


Help me spot the place where RCU free worker schedules itself back to 
free more objects - if I got the rationale here right?

Regards,

Tvrtko