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

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Message-ID: <20150930061241.GC3500@sudip-pc>
Date:	Wed, 30 Sep 2015 11:42:41 +0530
From:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:	Patrik Jakobsson <patrik.r.jakobsson@...il.com>
Cc:	David Airlie <airlied@...ux.ie>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/gma500: fix double freeing

On Tue, Sep 29, 2015 at 03:20:35PM +0200, Patrik Jakobsson wrote:
> On Thu, Sep 24, 2015 at 5:57 PM, Sudip Mukherjee
> <sudipm.mukherjee@...il.com> wrote:
> > On Wed, Sep 09, 2015 at 06:20:40PM +0530, Sudip Mukherjee wrote:
> >> 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>
> >> ---
> > Hi Patrik,
> > A gentle ping.
> >
> > regards
> > sudip
> 
> Hi, sorry for the late reply.
> 
> Why are we freeing the range twice in the first case?
I think,
if backing->stolen is true then backing is released using
psb_gtt_free_range() but if backing->stolen is false then the gem object
is freed but the backing is not yet freed. To free that backing
psb_gtt_free_range() has been called second time. My patch tried to fix
the possibility of backing->stolen being true and backing being freed 2
times.

regards
sudip

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