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

From Michal Hocko <mhocko@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH] mm: larger stack guard gap, between vmas
Date 2017-07-05 16:30 +0200
Message-ID <tZTtw-7s2-19@gated-at.bofh.it> (permalink)
References (5 earlier) <tZtz3-76W-9@gated-at.bofh.it> <tZuls-7Dd-23@gated-at.bofh.it> <tZF7c-6uZ-9@gated-at.bofh.it> <tZFAe-6E3-3@gated-at.bofh.it> <tZRBp-6aJ-27@gated-at.bofh.it>
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On Wed 05-07-17 13:19:40, Ben Hutchings wrote:
> On Tue, 2017-07-04 at 16:31 -0700, Linus Torvalds wrote:
> > On Tue, Jul 4, 2017 at 4:01 PM, Ben Hutchings <ben@decadent.org.uk>
> > wrote:
> > > 
> > > We have:
> > > 
> > > bottom = 0xff803fff
> > > sp =     0xffffb178
> > > 
> > > The relevant mappings are:
> > > 
> > > ff7fc000-ff7fd000 rwxp 00000000 00:00 0
> > > fffdd000-ffffe000 rw-p 00000000 00:00
> > > 0                                  [stack]
> > 
> > Ugh. So that stack is actually 8MB in size, but the alloca() is about
> > to use up almost all of it, and there's only about 28kB left between
> > "bottom" and that 'rwx' mapping.
> > 
> > Still, that rwx mapping is interesting: it is a single page, and it
> > really is almost exactly 8MB below the stack.
> > 
> > In fact, the top of stack (at 0xffffe000) is *exactly* 8MB+4kB from
> > the top of that odd one-page allocation (0xff7fd000).
> > 
> > Can you find out where that is allocated? Perhaps a breakpoint on
> > mmap, with a condition to catch that particular one?
> [...]
> 
> Found it, and it's now clear why only i386 is affected:
> http://hg.openjdk.java.net/jdk8/jdk8/hotspot/file/tip/src/os/linux/vm/os_linux.cpp#l4852
> http://hg.openjdk.java.net/jdk8/jdk8/hotspot/file/tip/src/os_cpu/linux_x86/vm/os_linux_x86.cpp#l881

This is really worrying. This doesn't look like a gap at all. It is a
mapping which actually contains a code and so we should absolutely not
allow to scribble over it. So I am afraid the only way forward is to
allow per process stack gap and run this particular program to have a
smaller gap. We basically have two ways. Either /proc/<pid>/$file or
a prctl inherited on exec. The later is a smaller code. What do you
think?
-- 
Michal Hocko
SUSE Labs

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Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-04 02:00 +0200
  Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-04 02:10 +0200
    Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-04 10:50 +0200
      Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-04 11:40 +0200
        Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-04 11:50 +0200
          Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-04 12:50 +0200
            Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-04 13:40 +0200
              Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-04 14:10 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-04 14:20 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-04 14:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-04 14:40 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ximin Luo <infinity0@debian.org> - 2017-07-04 16:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-04 16:50 +0200
              Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-04 18:00 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-04 19:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-04 20:40 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-04 20:50 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-04 21:10 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-04 20:50 +0200
              Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-04 18:20 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas John Haxby <john.haxby@oracle.com> - 2017-07-04 18:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-04 19:10 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-05 14:30 +0200
              Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-04 19:20 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-05 14:30 +0200
              Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-05 01:10 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-05 01:40 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-05 08:40 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-05 10:20 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-05 10:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-05 11:20 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-05 14:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-05 16:00 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-05 16:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-05 18:10 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-06 09:40 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-05 14:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-05 16:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-05 17:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-05 18:10 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-05 19:00 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-05 19:10 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-05 19:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-05 19:20 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-06 01:40 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-06 02:00 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-06 10:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-06 12:20 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Andy Lutomirski <luto@kernel.org> - 2017-07-05 18:20 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-05 18:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Andy Lutomirski <luto@kernel.org> - 2017-07-05 19:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-05 21:40 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-05 22:50 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Andy Lutomirski <luto@amacapital.net> - 2017-07-05 23:00 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Ben Hutchings <ben@decadent.org.uk> - 2017-07-06 02:00 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Andy Lutomirski <luto@kernel.org> - 2017-07-06 02:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Kees Cook <keescook@chromium.org> - 2017-07-06 02:00 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-06 02:00 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Andy Lutomirski <luto@kernel.org> - 2017-07-06 02:40 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-06 02:50 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Andy Lutomirski <luto@kernel.org> - 2017-07-06 02:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Kees Cook <keescook@chromium.org> - 2017-07-06 04:50 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-06 07:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Kevin Easton <kevin@guarana.org> - 2017-07-06 07:40 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-05 18:20 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-05 21:10 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Willy Tarreau <w@1wt.eu> - 2017-07-05 21:20 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-05 21:30 +0200
                Re: [PATCH] mm: larger stack guard gap, between vmas Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-05 21:20 +0200
                Re: [vs-plain] Re: [PATCH] mm: larger stack guard gap, between vmas "kseifried@redhat.com" <kseifried@redhat.com> - 2017-07-05 03:20 +0200
                Re: [vs-plain] Re: [PATCH] mm: larger stack guard gap, between vmas Solar Designer <solar@openwall.com> - 2017-07-05 16:20 +0200
        Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-04 12:50 +0200
          Re: [PATCH] mm: larger stack guard gap, between vmas Michal Hocko <mhocko@kernel.org> - 2017-07-04 13:00 +0200
  Re: [PATCH] mm: larger stack guard gap, between vmas Andy Lutomirski <luto@kernel.org> - 2017-07-04 02:30 +0200
  Re: [vs-plain] Re: [PATCH] mm: larger stack guard gap, between vmas John Haxby <john.haxby@oracle.com> - 2017-07-04 14:30 +0200

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