linux-kernel - Re: [PATCH] resource: Add NULL check in next

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Date:	Mon, 22 Sep 2014 08:46:15 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mikael Starvik <starvik@...s.com>,
	Jesper Nilsson <jesper.nilsson@...s.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] resource: Add NULL check in next_resource

On Mon, Sep 22, 2014 at 10:58:12AM -0400, Vivek Goyal wrote:
> On Sun, Sep 21, 2014 at 08:51:44AM -0700, Guenter Roeck wrote:
> > Commit 8c86e70acead ("resource: provide new functions to walk through
> > resources") adds a suble new requirement that iomem_resource.child must
> > not be NULL when walk_system_ram_range is called. This can cause a crash
> > if it turns out that there are no children. The crash ('Unable to handle
> > kernel NULL pointer dereference') is seen when trying to test a crisv32
> > image on kernels with this commit applied.
> > 
> > Fix by adding a NULL check into next_resource().
> > 
> > Fixes: 8c86e70acead ("resource: provide new functions to walk through resources")
> 
> One such problem was solved with following commit.
> 
> commit 800df627e2eabaf4a921d342a1d5162c843b7fc2
> Author: Vivek Goyal <vgoyal@...hat.com>
> Date:   Fri Aug 29 15:18:29 2014 -0700
> 
>     resource: fix the case of null pointer access
> 
> Do you have this patch applied in your tree?
> 
Bisect suggests that I did.

I know what happened: There was another problem that affected crisv32 in
v3.17-rc5, which I tried to bisect. Bisect result pointed to your commit,
but it wasn't the cause of the other problem. As a result, bisect did not
catch the real problem but the NULL pointer problem instead.

Please ignore my patch; I confirmed that commit 800df627e2ea already fixes
the problem I tried to fix.

Thanks,
Guenter
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