linux-kernel - [PATCH 3.16 127/294] drm: Release driver tracking before making the object available again

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Message-ID: <lsq.1510009382.540768621@decadent.org.uk>
Date:   Mon, 06 Nov 2017 23:03:02 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "David Airlie" <airlied@...ux.ie>,
        "Chris Wilson" <chris@...is-wilson.co.uk>,
        "Joonas Lahtinen" <joonas.lahtinen@...ux.intel.com>,
        "Daniel Vetter" <daniel.vetter@...ll.ch>,
        "Daniel Vetter" <daniel.vetter@...el.com>,
        "Ville Syrjälä" <ville.syrjala@...ux.intel.com>,
        "Thierry Reding" <treding@...dia.com>,
        "Rob Clark" <robdclark@...il.com>
Subject: [PATCH 3.16 127/294] drm: Release driver tracking before making
 the object available again

3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Chris Wilson <chris@...is-wilson.co.uk>

commit fe4600a548f2763dec91b3b27a1245c370ceee2a upstream.

This is the same bug as we fixed in commit f6cd7daecff5 ("drm: Release
driver references to handle before making it available again"), but now
the exposure is via the PRIME lookup tables. If we remove the
object/handle from the PRIME lut, then a new request for the same
object/fd will generate a new handle, thus for a short window that
object is known to userspace by two different handles. Fix this by
releasing the driver tracking before PRIME.

Fixes: 0ff926c7d4f0 ("drm/prime: add exported buffers to current fprivs
imported buffer list (v2)")
Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
Cc: David Airlie <airlied@...ux.ie>
Cc: Daniel Vetter <daniel.vetter@...el.com>
Cc: Rob Clark <robdclark@...il.com>
Cc: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc: Thierry Reding <treding@...dia.com>
Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170819120558.6465-1-chris@chris-wilson.co.uk
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/drm_gem.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -698,13 +698,13 @@ drm_gem_object_release_handle(int id, vo
 	struct drm_gem_object *obj = ptr;
 	struct drm_device *dev = obj->dev;
 
+	if (dev->driver->gem_close_object)
+		dev->driver->gem_close_object(obj, file_priv);
+
 	if (drm_core_check_feature(dev, DRIVER_PRIME))
 		drm_gem_remove_prime_handles(obj, file_priv);
 	drm_vma_node_revoke(&obj->vma_node, file_priv->filp);
 
-	if (dev->driver->gem_close_object)
-		dev->driver->gem_close_object(obj, file_priv);
-
 	drm_gem_object_handle_unreference_unlocked(obj);
 
 	return 0;