linux-kernel - Re: [PATCH] mpi: Avoid using freed pointer in mpi_lshift

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Message-ID: <alpine.LNX.2.00.1203150130370.22671@swampdragon.chaosbits.net>
Date:	Thu, 15 Mar 2012 01:33:04 +0100 (CET)
From:	Jesper Juhl <jj@...osbits.net>
To:	"Kasatkin, Dmitry" <dmitry.kasatkin@...el.com>
cc:	linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	James Morris <jmorris@...ei.org>
Subject: Re: [PATCH] mpi: Avoid using freed pointer in mpi_lshift_limbs()

On Tue, 13 Mar 2012, Kasatkin, Dmitry wrote:

> On Thu, Mar 1, 2012 at 11:33 PM, Jesper Juhl <jj@...osbits.net> wrote:
> >
> > Ping?
> >
> > On Mon, 6 Feb 2012, Jesper Juhl wrote:
> >
> >> At the start of the function we assign 'a->d' to 'ap'. Then we use the
> >> RESIZE_IF_NEEDED macro on 'a' - this may free 'a->d' and replace it
> >> with newly allocaetd storage. In that case, we'll be operating on
> >> freed memory further down in the function when we index into 'ap[]'.
> >> Since we don't actually need 'ap' until after the use of the
> >> RESIZE_IF_NEEDED macro we can just delay the assignment to it until
> >> after we've potentially resized, thus avoiding the issue.
> >>
> >> While I was there anyway I also changed the integer variable 'n' to be
> >> const. It might as well be since we only assign to it once and use it
> >> as a constant, and then the compiler will tell us if we ever assign to
> >> it in the future.
> >>
> >> Signed-off-by: Jesper Juhl <jj@...osbits.net>
> >> ---
[...]
> Hello,
> 
> I was travelling last week.
> I will review the patch now..
> 

:-) Thanks. No rush, I'd just like to see the fix included at some point 
if you agree that it is correct - just wondered at the "~1 month no 
response".


> Thanks,
> Dmitry
> 

-- 
Jesper Juhl <jj@...osbits.net>       http://www.chaosbits.net/
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