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Groups > linux.kernel > #1505329

Re: bio linked list corruption.

From Andy Lutomirski <luto@amacapital.net>
Newsgroups linux.kernel
Subject Re: bio linked list corruption.
Date 2016-10-21 01:30 +0200
Message-ID <suuWB-5LC-1@gated-at.bofh.it> (permalink)
References (6 earlier) <stMLT-1jl-3@gated-at.bofh.it> <stNyi-1V9-3@gated-at.bofh.it> <suutA-5mC-33@gated-at.bofh.it> <suuDg-5F6-9@gated-at.bofh.it> <suuDg-5F6-7@gated-at.bofh.it>
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On Thu, Oct 20, 2016 at 4:03 PM, Dave Jones <davej@codemonkey.org.uk> wrote:
> On Thu, Oct 20, 2016 at 04:01:12PM -0700, Andy Lutomirski wrote:
>  > On Thu, Oct 20, 2016 at 3:50 PM, Dave Jones <davej@codemonkey.org.uk> wrote:
>  > > On Tue, Oct 18, 2016 at 06:05:57PM -0700, Andy Lutomirski wrote:
>  > >
>  > >  > One possible debugging approach would be to change:
>  > >  >
>  > >  > #define NR_CACHED_STACKS 2
>  > >  >
>  > >  > to
>  > >  >
>  > >  > #define NR_CACHED_STACKS 0
>  > >  >
>  > >  > in kernel/fork.c and to set CONFIG_DEBUG_PAGEALLOC=y.  The latter will
>  > >  > force an immediate TLB flush after vfree.
>  > >
>  > > I can give that idea some runtime, but it sounds like this a case where
>  > > we're trying to prove a negative, and that'll just run and run ? In which case I
>  > > might do this when I'm travelling on Sunday.
>  >
>  > The idea is that the stack will be free and unmapped immediately upon
>  > process exit if configured like this so that bogus stack accesses (by
>  > the CPU, not DMA) would OOPS immediately.
>
> oh, misparsed. ok, I can definitely get behind that idea then.
> I'll do that next.
>

It could be worth trying this, too:

https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=x86/vmap_stack&id=174531fef4e8

It occurred to me that the current code is a little bit fragile.

--Andy

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Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-19 00:50 +0200
  Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-19 01:40 +0200
    Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-19 02:20 +0200
      Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-19 02:30 +0200
        Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-21 00:50 +0200
      Re: bio linked list corruption. Andy Lutomirski <luto@kernel.org> - 2016-10-19 03:10 +0200
        Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-21 01:00 +0200
          Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-21 01:10 +0200
            Re: bio linked list corruption. Andy Lutomirski <luto@amacapital.net> - 2016-10-21 01:30 +0200
              Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-21 22:10 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-21 22:30 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-21 23:20 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-22 17:30 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-24 06:50 +0200
                Re: bio linked list corruption. Andy Lutomirski <luto@amacapital.net> - 2016-10-24 22:10 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-24 22:50 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-24 23:20 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-25 00:00 +0200
                Re: bio linked list corruption. Andy Lutomirski <luto@amacapital.net> - 2016-10-25 00:50 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-25 02:10 +0200
                Re: bio linked list corruption. Andy Lutomirski <luto@amacapital.net> - 2016-10-25 03:20 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-26 02:30 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-26 03:40 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-26 03:40 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-26 18:40 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-26 18:50 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-26 20:20 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-26 20:50 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-26 21:10 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-27 00:10 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-27 00:30 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-27 00:50 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-27 01:00 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-27 01:00 +0200
                Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-27 01:10 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-27 01:50 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-27 01:10 +0200
                Re: bio linked list corruption. Dave Jones <davej@codemonkey.org.uk> - 2016-10-27 01:10 +0200
          Re: bio linked list corruption. Andy Lutomirski <luto@amacapital.net> - 2016-10-21 01:10 +0200
    Re: bio linked list corruption. Philipp Hahn <pmhahn@pmhahn.de> - 2016-10-19 19:10 +0200
      Re: bio linked list corruption. Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-19 19:50 +0200
        Re: bio linked list corruption. Ingo Molnar <mingo@kernel.org> - 2016-10-20 09:00 +0200
          Re: bio linked list corruption. Thomas Gleixner <tglx@linutronix.de> - 2016-10-20 09:30 +0200

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