-----Original Message-----
From: Chris Wilson <redacted>
Sent: Thursday, July 23, 2020 10:21 AM
To: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org; Chris Wilson <redacted>;
Tang, CQ [off-list ref]; Vetter, Daniel [off-list ref];
stable@vger.kernel.org
Subject: [PATCH 2/3] drm/i915/gem: Move context decoupling from
postclose to preclose

Since the GEM contexts refer to other GEM state, we need to nerf those
pointers before that state is freed during drm_gem_release(). We need to
move i915_gem_context_close() from the postclose callback to the preclose.

In particular, debugfs likes to peek into the GEM contexts, and from there
peek at the drm core objects. If the context is closed during the peeking, we
may attempt to dereference a stale core object.

Signed-off-by: Chris Wilson <redacted>
Cc: CQ Tang <redacted>
Cc: Daniel Vetter <redacted>
Cc: stable@vger.kernel.org
---
 drivers/gpu/drm/i915/i915_drv.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c

b/drivers/gpu/drm/i915/i915_drv.c index 5fd5af4bc855..15242a8c70f7 100644

--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c

@@ -1114,11 +1114,15 @@ static void i915_driver_lastclose(struct

drm_device *dev)
 	vga_switcheroo_process_delayed_switch();
 }

+static void i915_driver_preclose(struct drm_device *dev, struct
+drm_file *file) {
+	i915_gem_context_close(file);
+}
+
 static void i915_driver_postclose(struct drm_device *dev, struct drm_file
*file)  {
 	struct drm_i915_file_private *file_priv = file->driver_priv;

-	i915_gem_context_close(file);
 	i915_gem_release(dev, file);

 	kfree_rcu(file_priv, rcu);

@@ -1850,6 +1854,7 @@ static struct drm_driver driver = {
 	.release = i915_driver_release,
 	.open = i915_driver_open,
 	.lastclose = i915_driver_lastclose,
+	.preclose  = i915_driver_preclose,
 	.postclose = i915_driver_postclose,

 	.gem_close_object = i915_gem_close_object,
--

2.20.1