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

[Ville Syrjälä]

On Mon, Oct 24, 2022 at 10:08:29AM +0200, Das, Nirmoy wrote:
> 
> On 10/21/2022 6:34 PM, Ville Syrjälä wrote:
> > On Fri, Sep 23, 2022 at 09:35:14AM +0200, 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.
> > shard-snb is stil hitting the mm.shrink_count WARNn reliably,
> > and things go downhill after that.
> 
> 
> Looks better now again. Going to look into that.

Looks to be still hitting it occasionally in module reload tests:
https://intel-gfx-ci.01.org/tree/drm-tip/IGT_7033/shard-snb5/igt@i915_module_load@reload.html
https://intel-gfx-ci.01.org/tree/drm-tip/IGT_7035/shard-snb7/igt@perf_pmu@module-unload.html

> 
> 
> Thanks,
> 
> Nirmoy
> 
> >
> >> Suggested-by: Chris Wilson <chris.p.wilson at intel.com>
> >> Acked-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >> Signed-off-by: Nirmoy Das <nirmoy.das at 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 88df9a35e0fe..7541028caebd 100644
> >> --- a/drivers/gpu/drm/i915/i915_gem.c
> >> +++ b/drivers/gpu/drm/i915/i915_gem.c
> >> @@ -1278,7 +1278,7 @@ 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);
> >> -- 
> >> 2.37.3

-- 
Ville Syrjälä
Intel