linux-kernel - [PATCH] drm/gma500: fix double freeing

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Date:	Wed,  9 Sep 2015 18:20:40 +0530
From:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:	David Airlie <airlied@...ux.ie>,
	Daniel Vetter <daniel.vetter@...ll.ch>
Cc:	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	Sudip Mukherjee <sudipm.mukherjee@...il.com>
Subject: [PATCH] drm/gma500: fix double freeing

If backing->stolen is true then we were freeing backing by calling
psb_gtt_free_range() but we called it again after unlocking the mutex.
Lets make it NULL after freeing in psb_gtt_free_range() and check for
NULL before calling the function for the second time.

Signed-off-by: Sudip Mukherjee <sudip@...torindia.org>
---
 drivers/gpu/drm/gma500/framebuffer.c | 3 ++-
 drivers/gpu/drm/gma500/gtt.c         | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/gma500/framebuffer.c b/drivers/gpu/drm/gma500/framebuffer.c
index 2eaf1b3..381d7af 100644
--- a/drivers/gpu/drm/gma500/framebuffer.c
+++ b/drivers/gpu/drm/gma500/framebuffer.c
@@ -474,7 +474,8 @@ out_unref:
 	drm_fb_helper_release_fbi(&fbdev->psb_fb_helper);
 out_err1:
 	mutex_unlock(&dev->struct_mutex);
-	psb_gtt_free_range(dev, backing);
+	if (backing)
+		psb_gtt_free_range(dev, backing);
 	return ret;
 }
 
diff --git a/drivers/gpu/drm/gma500/gtt.c b/drivers/gpu/drm/gma500/gtt.c
index ce015db..8130fa8 100644
--- a/drivers/gpu/drm/gma500/gtt.c
+++ b/drivers/gpu/drm/gma500/gtt.c
@@ -385,6 +385,7 @@ void psb_gtt_free_range(struct drm_device *dev, struct gtt_range *gt)
 	WARN_ON(gt->in_gart && !gt->stolen);
 	release_resource(&gt->resource);
 	kfree(gt);
+	gt = NULL;
 }
 
 static void psb_gtt_alloc(struct drm_device *dev)
-- 
1.9.1

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