linux-kernel - [PATCH 3.16.y-ckt 140/180] drm/i915: avoid deadlock on failure paths in __intel_framebuffer

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Date:	Wed,  3 Feb 2016 22:32:26 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Alexey Khoroshilov <khoroshilov@...ras.ru>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 140/180] drm/i915: avoid deadlock on failure paths in __intel_framebuffer_create()

3.16.7-ckt24 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Alexey Khoroshilov <khoroshilov@...ras.ru>

commit 6ccb81f2171ab48592946efab0ce0fd41978f4ba upstream.

Since a8bb6818270c __intel_framebuffer_create() is called
with struct_mutex held, so it should use drm_gem_object_unreference()
instead of drm_gem_object_unreference_unlocked().

Found by Linux Driver Verification project (linuxtesting.org).

This regression has been introduced in

commit a8bb6818270c32126dba0fd2ddb139d885c5687d
Author: Daniel Vetter <daniel.vetter@...ll.ch>
Date:   Mon Feb 10 18:00:39 2014 +0100

    drm/i915: Fix error path leak in fbdev fb allocation

Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/gpu/drm/i915/intel_display.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index b019c563a787..0d68c70368ff 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8220,7 +8220,7 @@ __intel_framebuffer_create(struct drm_device *dev,
 
 	intel_fb = kzalloc(sizeof(*intel_fb), GFP_KERNEL);
 	if (!intel_fb) {
-		drm_gem_object_unreference_unlocked(&obj->base);
+		drm_gem_object_unreference(&obj->base);
 		return ERR_PTR(-ENOMEM);
 	}
 
@@ -8230,7 +8230,7 @@ __intel_framebuffer_create(struct drm_device *dev,
 
 	return &intel_fb->base;
 err:
-	drm_gem_object_unreference_unlocked(&obj->base);
+	drm_gem_object_unreference(&obj->base);
 	kfree(intel_fb);
 
 	return ERR_PTR(ret);