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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 2017-07-04 21:10 +0200
Message-ID <tZBmV-42R-5@gated-at.bofh.it> (permalink)
References (5 earlier) <tZyp3-1UF-13@gated-at.bofh.it> <tZzO9-2WF-7@gated-at.bofh.it> <tZATT-3Aa-11@gated-at.bofh.it> <tZB3z-3Dr-11@gated-at.bofh.it> <tZB3z-3Dr-9@gated-at.bofh.it>
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On Tue, Jul 04, 2017 at 11:47:37AM -0700, Linus Torvalds wrote:
> Let's
> say that you are using lots of threads, so that you know your stack
> space is limited. What you do is to use MAP_FIXED a lot, and you lay
> out your stacks fairly densely (with each other, but also possibly
> with other mappings), with that PROT_NONE redzoning mapping in between
> the "dense" allocations.
> 
> So when the kernel wants to grow the stack, it finds the PROT_NONE
> redzone mapping - but there's possibly other maps right under it, so
> the stack_guard_gap still hits other mappings.
(...)

OK I didn't get that use case, that totally makes sense indeed! So
now we use PROT_NONE not as something that must be skipped to find
the unmapped area but as a hint that the application apparently
wants the stack to stop here.

Thanks for this clear explanation!

Willy

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Thread

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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