linux-kernel - Re: [PATCH v2] powerpc/mpc5xxx: Avoid dereferencing potentially freed memory

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Message-ID: <20151016071552.GB20310@visitor2.iram.es>
Date:	Fri, 16 Oct 2015 09:15:52 +0200
From:	Gabriel Paubert <paubert@...m.es>
To:	Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:	Michael Ellerman <mpe@...erman.id.au>,
	kernel-janitors@...r.kernel.org, paulus@...ba.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] powerpc/mpc5xxx: Avoid dereferencing potentially
 freed memory

On Fri, Oct 16, 2015 at 08:20:13AM +0200, Christophe JAILLET wrote:
> Le 15/10/2015 08:36, Michael Ellerman a écrit :
> >On Thu, 2015-10-15 at 07:56 +0200, Christophe JAILLET wrote:
> >>Use 'of_property_read_u32()' instead of 'of_get_property()'+pointer
> >>dereference in order to avoid access to potentially freed memory.
> >>
> >>Use 'of_get_next_parent()' to simplify the while() loop and avoid the
> >>need of a temp variable.
> >>
> >>Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> >>---
> >>v2: Use of_property_read_u32 instead of of_get_property+pointer dereference
> >>*** Untested ***
> >Thanks.
> >
> >Can someone with an mpc5xxx test this?
> >
> >cheers
> >
> 
> Hi,
> I don't think it is an issue, but while looking at another similar
> patch, I noticed that the proposed patch adds a call to
> be32_to_cpup() (within of_property_read_u32).
> Apparently, powerPC is a BE architecture, so this call should be a no-op.

Sadly no more. 32 bit is BE only, but 64 bit can be either BEtter or
LEsser.

    Gabriel
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