drm/i915: Check before removing mm notifier

Error in mmu_interval_notifier_insert() can leave a NULL
notifier.mm pointer. Catch that and return early.

Fixes: ed29c2691188 ("drm/i915: Fix userptr so we do not have to worry about obj->mm.lock, v7.")
Cc: <stable@vger.kernel.org> # v5.13+
[tursulin: Added Fixes and cc stable.]
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>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240219125047.28906-1-nirmoy.das@intel.com
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
(cherry picked from commit db7bbd13f08774cde0332c705f042e327fe21e73)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
index 1d3ebdf4069b5d0fea98aefdb2b1609f82b9650e..c08b67593565c5827d4555e70b88b083e97172d9 100644 (file)
--- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -379,6 +379,9 @@ i915_gem_userptr_release(struct drm_i915_gem_object *obj)
 {
        GEM_WARN_ON(obj->userptr.page_ref);
 
+       if (!obj->userptr.notifier.mm)
+               return;
+
        mmu_interval_notifier_remove(&obj->userptr.notifier);
        obj->userptr.notifier.mm = NULL;
 }