Commit dcb1394e authored Jul 04, 2015 by Lukas Wunner Committed by Jani Nikula Nov 09, 2015

drm/i915: On fb alloc failure, unref gem object where it gets refed



Currently when allocating a framebuffer fails, the gem object gets
unrefed at the bottom of the call stack in __intel_framebuffer_create,
not where it gets refed, which is in intel_framebuffer_create_for_mode
(via i915_gem_alloc_object) and in intel_user_framebuffer_create
(via drm_gem_object_lookup).

This invites mistakes: __intel_framebuffer_create is also called from
intelfb_alloc, and as discovered by Tvrtko Ursulin, a double unref
was introduced there with a8bb6818 ("drm/i915: Fix error path leak
in fbdev fb allocation").

As suggested by Ville Syrjälä, fix the double unref and improve code
clarity by moving the unref away from __intel_framebuffer_create to
where the gem object gets refed.

Based on Tvrtko Ursulin's original v2.

v3: On fb alloc failure, unref gem object where it gets refed,
    fix double unref in separate commit (Ville Syrjälä)

v4: Lock struct_mutex on unref (Chris Wilson)

v5: Rebase on drm-intel-nightly 2015y-09m-01d-09h-06m-08s UTC,
    rephrase commit message (Jani Nicula)

Tested-by: Pierre Moreau <pierre.morrow@free.fr>
    [MBP  5,3 2009  nvidia MCP79 + G96        pre-retina]
Tested-by: Paul Hordiienko <pvt.gord@gmail.com>
    [MBP  6,2 2010  intel ILK + nvidia GT216  pre-retina]
Tested-by: William Brown <william@blackhats.net.au>
    [MBP  8,2 2011  intel SNB + amd turks     pre-retina]
Tested-by: Lukas Wunner <lukas@wunner.de>
    [MBP  9,1 2012  intel IVB + nvidia GK107  pre-retina]
Tested-by: Bruno Bierbaumer <bruno@bierbaumer.net>
    [MBP 11,3 2013  intel HSW + nvidia GK107  retina]

Fixes: a8bb6818 ("drm/i915: Fix error path leak in fbdev fb
    allocation")
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/2161c5062ef5d6458f8ae14d924a26d4d1dba317.1446892879.git.lukas@wunner.de


Signed-off-by: Jani Nikula <jani.nikula@intel.com>

parent e588fa18

drivers/gpu/drm/i915/intel_display.c

+14 −7

Original line number	Diff line number	Diff line
		@@ -10065,20 +10065,17 @@ __intel_framebuffer_create(struct drm_device *dev,
		int ret;

		intel_fb = kzalloc(sizeof(*intel_fb), GFP_KERNEL);
		if (!intel_fb) {
		drm_gem_object_unreference(&obj->base);
		if (!intel_fb)
		return ERR_PTR(-ENOMEM);
		}

		ret = intel_framebuffer_init(dev, intel_fb, mode_cmd, obj);
		if (ret)
		goto err;

		return &intel_fb->base;

		err:
		drm_gem_object_unreference(&obj->base);
		kfree(intel_fb);

		return ERR_PTR(ret);
		}

		@@ -10118,6 +10115,7 @@ intel_framebuffer_create_for_mode(struct drm_device *dev,
		struct drm_display_mode *mode,
		int depth, int bpp)
		{
		struct drm_framebuffer *fb;
		struct drm_i915_gem_object *obj;
		struct drm_mode_fb_cmd2 mode_cmd = { 0 };

		@@ -10132,7 +10130,11 @@ intel_framebuffer_create_for_mode(struct drm_device *dev,
		bpp);
		mode_cmd.pixel_format = drm_mode_legacy_fb_format(bpp, depth);

		return intel_framebuffer_create(dev, &mode_cmd, obj);
		fb = intel_framebuffer_create(dev, &mode_cmd, obj);
		if (IS_ERR(fb))
		drm_gem_object_unreference_unlocked(&obj->base);

		return fb;
		}

		static struct drm_framebuffer *
		@@ -14530,6 +14532,7 @@ intel_user_framebuffer_create(struct drm_device *dev,
		struct drm_file *filp,
		struct drm_mode_fb_cmd2 *mode_cmd)
		{
		struct drm_framebuffer *fb;
		struct drm_i915_gem_object *obj;

		obj = to_intel_bo(drm_gem_object_lookup(dev, filp,
		@@ -14537,7 +14540,11 @@ intel_user_framebuffer_create(struct drm_device *dev,
		if (&obj->base == NULL)
		return ERR_PTR(-ENOENT);

		return intel_framebuffer_create(dev, mode_cmd, obj);
		fb = intel_framebuffer_create(dev, mode_cmd, obj);
		if (IS_ERR(fb))
		drm_gem_object_unreference_unlocked(&obj->base);

		return fb;
		}

		#ifndef CONFIG_DRM_FBDEV_EMULATION