linux-kernel - Re: [PATCH 17/21] MSI: Clear the irq

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Message-Id: <1174604508.5401.7.camel@concordia.ozlabs.ibm.com>
Date:	Fri, 23 Mar 2007 10:01:48 +1100
From:	Michael Ellerman <michael@...erman.id.au>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	linux-pci@...ey.karlin.mff.cuni.cz,
	Greg Kroah-Hartman <greg@...ah.com>,
	"David S. Miller" <davem@...emloft.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linux-kernel@...r.kernel.org, Andrew Morton <akpm@...l.org>,
	daniel.e.wolstenholme@...el.com
Subject: Re: [PATCH 17/21] MSI: Clear the irq_desc's msi pointer on free

On Thu, 2007-03-22 at 08:23 -0600, Eric W. Biederman wrote:
> Michael Ellerman <michael@...erman.id.au> writes:
> 
> > Currently we never clear the msi_desc pointer in the irq_desc. This
> > leaves us with a pointer to free'ed memory hanging around. No one seems
> > to have hit this, so presumably other parts of the code are protecting
> > us from ever using the stale pointer .. or we're just lucky, we should
> > still clear it.
> 
> Hmm.  Maybe.  Currently this is done in dynamic_irq_cleanup,
> at least for everything except sparc64.

OK, I missed that. I still think we should do it here, otherwise there's
a window, however small, where the msi_desc pointer is pointing at freed
memory.

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

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