linux-kernel - Re: [PATCH 3.2 056/185] mm: ensure get_unmapped_area() returns higher address than mmap_min

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Date:	Mon, 6 Jan 2014 12:32:07 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	Akira Takeuchi <takeuchi.akr@...panasonic.com>
Cc:	Ben Hutchings <ben@...adent.org.uk>, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, akpm@...ux-foundation.org,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Kiyoshi Owada <owada.kiyoshi@...panasonic.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 3.2 056/185] mm: ensure get_unmapped_area() returns
 higher address than mmap_min_addr

On Mon, Jan 06, 2014 at 07:19:10PM +0900, Akira Takeuchi wrote:
> On Fri, 03 Jan 2014 04:26:43 +0000
> Ben Hutchings <ben@...adent.org.uk> wrote:
> 
> > On Sun, 2013-12-29 at 03:08 +0100, Ben Hutchings wrote:
> > > 3.2.54-rc1 review patch.  If anyone has any objections, please let me know.
> > > 
> > > ------------------
> > > 
> > > From: Akira Takeuchi <takeuchi.akr@...panasonic.com>
> > > 
> > > commit 2afc745f3e3079ab16c826be4860da2529054dd2 upstream.
> > [...]
> > > [bwh: Backported to 3.2:
> > >  As we do not have vm_unmapped_area(), make arch_get_unmapped_area_topdown()
> > >  calculate the lower limit for the new area's end address and then compare
> > >  addresses with this instead of with len.  In the process, fix an off-by-one
> > >  error which could result in returning 0 if mm->mmap_base == len.]
> > 
> > I'm dropping this as I have no good way to test the backport (it's not
> > used on x86) and I didn't get any confirmation that it's right.
> 
> I'm sorry for delayed reply.
> 
> Your backport seems right.
> Additionally, I've confirmed the problem is resolved by your backport patch.

Sorry I'm also late for this review.

I guess this means the backport I made for the 3.5 kernel (and released on
3.5.7.26) is incorrect:

http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=commitdiff;h=745545489d25d1b9ecf2d78a8f9a31a362806d2d

Akira, could you please confirm if this is the case so that I revert it in
next release?

Cheers,
--
Luis
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