Re: [PATCH] mm: larger stack guard gap, between vmas

From	Willy Tarreau <w@1wt.eu>
Newsgroups	linux.kernel
Subject	Re: [PATCH] mm: larger stack guard gap, between vmas
Date	2017-06-22 15:30 +0200
Message-ID	<tValj-5i5-7@gated-at.bofh.it> (permalink)
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On Thu, Jun 22, 2017 at 03:10:34PM +0200, Willy Tarreau wrote:
> On Thu, Jun 22, 2017 at 01:58:11PM +0100, Ben Hutchings wrote:
> > On Thu, 2017-06-22 at 14:46 +0200, Willy Tarreau wrote:
> > > On Thu, Jun 22, 2017 at 01:30:45PM +0100, Ben Hutchings wrote:
> > > > Here's my attempt at a backport to 3.2.  This is only tested on
> > > > x86_64 and I think I should introduce local variables for
> > > > vma_start_gap() in a few places.  I had to cherry-pick commit
> > > > 09884964335e "mm: do not grow the stack vma just because of an overrun
> > > > on preceding vma" before this one (which was a clean cherry-pick).
> > > 
> > > Ben, I can't apply it on top of 3.2.89 + the patch above, do you have
> > > any other patch in your local branch ? For example the patch tries to
> > > modify a hunk starting at line 183 of arch/arm/mm/mmap.c while the one
> > > I'm having here ends at line 159.
> > 
> > Sorry, yes, I did this on top of the Debian 3.2 branch and that *does*
> > have a patch to arch/arm/mm/mmap.c that I had forgotten about (commit
> > 7dbaa466780a "ARM: 7169/1: topdown mmap support").  I think you can
> > just drop the changes in ARM's arch_get_unmapped_area_topdown().
> 
> Thanks, I've just applied this one and it's building now. I'll run the
> same checks I did for 3.10.

So I tested this with gap.c on an i386 VM running 2G/2G split memory, all
went fine. It properly stopped the stack growth before colliding with anon
pages.

I noticed that you included Hugh's last fix in it (mm: fix new crash in
unmapped_area_topdown). You'll also need Helge's fix bd726c90b ("Allow
stack to grow up to address space limit"), which applies without issues
on top of your patch.

I would have happily tested on an ARM board but I don't seem to have
3.2-compatible ARM boards with 2G of RAM :-/

Willy

Thread

Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-06-22 14:50 +0200
  Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-06-22 15:10 +0200
    Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-06-22 15:20 +0200
      Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-06-22 15:30 +0200
    Re: [vs-plain] Re: [PATCH] mm: larger stack guard gap, between vmas Levente Polyak <anthraxx@archlinux.org> - 2017-06-22 16:00 +0200
      Re: [vs-plain] Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-06-22 16:10 +0200
        Re: [vs-plain] Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-06-22 16:20 +0200
          Re: [vs-plain] Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-06-22 16:40 +0200
            Re: [vs-plain] Re: [PATCH] mm: larger stack guard gap, between vmas Andy Lutomirski <luto@kernel.org> - 2017-06-23 05:20 +0200
              Re: [vs-plain] Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-06-23 06:50 +0200
          Re: [vs-plain] Re: [PATCH] mm: larger stack guard gap, between vmas Helge Deller <deller@gmx.de> - 2017-06-22 23:30 +0200

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