Re: [PATCH] drm/i915: check before removing mm notifier

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Mon, Feb 19, 2024 at 01:50:47PM +0100, Nirmoy Das wrote:
> Error in mmu_interval_notifier_insert() can leave a NULL
> notifier.mm pointer. Catch that and return early.
> 
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Cc: Shawn Lee <shawn.c.lee@intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> index 0e21ce9d3e5a..61abfb505766 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> @@ -349,6 +349,9 @@ i915_gem_userptr_release(struct drm_i915_gem_object *obj)
>  {
>  	GEM_WARN_ON(obj->userptr.page_ref);
>  
> +	if (!obj->userptr.notifier.mm)
> +		return;
> +

hmmm... right, it looks that we need this protection. But...

I mean, feel free to use
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

for this patch,

but I believe that if this mmu insert failed we might have other
deeper problems like when checking i915_gem_object_is_userptr() ?

No?!

>  	mmu_interval_notifier_remove(&obj->userptr.notifier);
>  	obj->userptr.notifier.mm = NULL;
>  }
> -- 
> 2.42.0
>