4 files changed, 39 insertions, 18 deletions

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 7f2831efc798..e4b78ab4773b 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1688,6 +1688,10 @@ void i915_gem_init__contexts(struct drm_i915_private *i915)
 	init_contexts(&i915->gem.contexts);
 }
 
+/*
+ * Note that this implicitly consumes the ctx reference, by placing
+ * the ctx in the context_xa.
+ */
 static void gem_context_register(struct i915_gem_context *ctx,
 				 struct drm_i915_file_private *fpriv,
 				 u32 id)
@@ -1703,10 +1707,6 @@ static void gem_context_register(struct i915_gem_context *ctx,
 	snprintf(ctx->name, sizeof(ctx->name), "%s[%d]",
 		 current->comm, pid_nr(ctx->pid));
 
-	/* And finally expose ourselves to userspace via the idr */
-	old = xa_store(&fpriv->context_xa, id, ctx, GFP_KERNEL);
-	WARN_ON(old);
-
 	spin_lock(&ctx->client->ctx_lock);
 	list_add_tail_rcu(&ctx->client_link, &ctx->client->ctx_list);
 	spin_unlock(&ctx->client->ctx_lock);
@@ -1714,6 +1714,10 @@ static void gem_context_register(struct i915_gem_context *ctx,
 	spin_lock(&i915->gem.contexts.lock);
 	list_add_tail(&ctx->link, &i915->gem.contexts.list);
 	spin_unlock(&i915->gem.contexts.lock);
+
+	/* And finally expose ourselves to userspace via the idr */
+	old = xa_store(&fpriv->context_xa, id, ctx, GFP_KERNEL);
+	WARN_ON(old);
 }
 
 int i915_gem_context_open(struct drm_i915_private *i915,
@@ -1857,11 +1861,19 @@ static int get_ppgtt(struct drm_i915_file_private *file_priv,
 	vm = ctx->vm;
 	GEM_BUG_ON(!vm);
 
+	/*
+	 * Get a reference for the allocated handle.  Once the handle is
+	 * visible in the vm_xa table, userspace could try to close it
+	 * from under our feet, so we need to hold the extra reference
+	 * first.
+	 */
+	i915_vm_get(vm);
+
 	err = xa_alloc(&file_priv->vm_xa, &id, vm, xa_limit_32b, GFP_KERNEL);
-	if (err)
+	if (err) {
+		i915_vm_put(vm);
 		return err;
-
-	i915_vm_get(vm);
+	}
 
 	GEM_BUG_ON(id == 0); /* reserved for invalid/unassigned ppgtt */
 	args->value = id;
@@ -2199,14 +2211,22 @@ finalize_create_context_locked(struct drm_i915_file_private *file_priv,
 	if (IS_ERR(ctx))
 		return ctx;
 
+	/*
+	 * One for the xarray and one for the caller.  We need to grab
+	 * the reference *prior* to making the ctx visble to userspace
+	 * in gem_context_register(), as at any point after that
+	 * userspace can try to race us with another thread destroying
+	 * the context under our feet.
+	 */
+	i915_gem_context_get(ctx);
+
 	gem_context_register(ctx, file_priv, id);
 
 	old = xa_erase(&file_priv->proto_context_xa, id);
 	GEM_BUG_ON(old != pc);
 	proto_context_close(file_priv->dev_priv, pc);
 
-	/* One for the xarray and one for the caller */
-	return i915_gem_context_get(ctx);
+	return ctx;
 }
 
 struct i915_gem_context *
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index 0ad44f3868de..c7c252d4d366 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -697,7 +697,7 @@ insert:
 	GEM_BUG_ON(lookup_mmo(obj, mmap_type) != mmo);
 out:
 	if (file)
-		drm_vma_node_allow(&mmo->vma_node, file);
+		drm_vma_node_allow_once(&mmo->vma_node, file);
 	return mmo;
 
 err:
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_tiling.c b/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
index fd42b89b7162..bc21b1c2350a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
@@ -305,10 +305,6 @@ i915_gem_object_set_tiling(struct drm_i915_gem_object *obj,
 	spin_unlock(&obj->vma.lock);
 
 	obj->tiling_and_stride = tiling | stride;
-	i915_gem_object_unlock(obj);
-
-	/* Force the fence to be reacquired for GTT access */
-	i915_gem_object_release_mmap_gtt(obj);
 
 	/* Try to preallocate memory required to save swizzling on put-pages */
 	if (i915_gem_object_needs_bit17_swizzle(obj)) {
@@ -321,6 +317,11 @@ i915_gem_object_set_tiling(struct drm_i915_gem_object *obj,
 		obj->bit_17 = NULL;
 	}
 
+	i915_gem_object_unlock(obj);
+
+	/* Force the fence to be reacquired for GTT access */
+	i915_gem_object_release_mmap_gtt(obj);
+
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
index beaf27e09e8a..977dead10ab5 100644
--- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
+++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
@@ -1847,7 +1847,7 @@ static int igt_shrink_thp(void *arg)
 			I915_SHRINK_ACTIVE);
 	i915_vma_unpin(vma);
 	if (err)
-		goto out_put;
+		goto out_wf;
 
 	/*
 	 * Now that the pages are *unpinned* shrinking should invoke
@@ -1863,19 +1863,19 @@ static int igt_shrink_thp(void *arg)
 		pr_err("unexpected pages mismatch, should_swap=%s\n",
 		       str_yes_no(should_swap));
 		err = -EINVAL;
-		goto out_put;
+		goto out_wf;
 	}
 
 	if (should_swap == (obj->mm.page_sizes.sg || obj->mm.page_sizes.phys)) {
 		pr_err("unexpected residual page-size bits, should_swap=%s\n",
 		       str_yes_no(should_swap));
 		err = -EINVAL;
-		goto out_put;
+		goto out_wf;
 	}
 
 	err = i915_vma_pin(vma, 0, 0, flags);
 	if (err)
-		goto out_put;
+		goto out_wf;
 
 	while (n--) {
 		err = cpu_check(obj, n, 0xdeadbeaf);