From 3220c3b2115102bb35f8f07d90d2989a3f5eb452 Mon Sep 17 00:00:00 2001
From: Karol Herbst <kherbst@redhat.com>
Date: Wed, 20 Apr 2022 11:57:20 +0200
Subject: drm/i915: Fix race in __i915_vma_remove_closed
Git-commit: 3220c3b2115102bb35f8f07d90d2989a3f5eb452
Patch-mainline: v5.18-rc7
References: bsc#1190497

i915_vma_reopen checked if the vma is closed before without taking the
lock. So multiple threads could attempt removing the vma.

Instead the lock needs to be taken before actually checking.

v2: move struct declaration

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v5.3+
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5732
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Fixes: 155ab8836caa ("drm/i915: Move object close under its own lock")
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220420095720.3331609-1-kherbst@redhat.com
(cherry picked from commit 1df1c79cbb7ac9bf148930be3418973c76ba8dde)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/i915/i915_vma.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -1103,22 +1103,23 @@ void i915_vma_close(struct i915_vma *vma
 
 static void __i915_vma_remove_closed(struct i915_vma *vma)
 {
-	struct intel_gt *gt = vma->vm->gt;
-
-	spin_lock_irq(&gt->closed_lock);
 	list_del_init(&vma->closed_link);
-	spin_unlock_irq(&gt->closed_lock);
 }
 
 void i915_vma_reopen(struct i915_vma *vma)
 {
+	struct intel_gt *gt = vma->vm->gt;
+
+	spin_lock_irq(&gt->closed_lock);
 	if (i915_vma_is_closed(vma))
 		__i915_vma_remove_closed(vma);
+	spin_unlock_irq(&gt->closed_lock);
 }
 
 void i915_vma_release(struct kref *ref)
 {
 	struct i915_vma *vma = container_of(ref, typeof(*vma), ref);
+	struct intel_gt *gt = vma->vm->gt;
 
 	if (drm_mm_node_allocated(&vma->node)) {
 		mutex_lock(&vma->vm->mutex);
@@ -1139,7 +1140,9 @@ void i915_vma_release(struct kref *ref)
 		spin_unlock(&obj->vma.lock);
 	}
 
+	spin_lock_irq(&gt->closed_lock);
 	__i915_vma_remove_closed(vma);
+	spin_unlock_irq(&gt->closed_lock);
 	i915_vm_put(vma->vm);
 
 	i915_active_fini(&vma->active);