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Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core)

From Andy Lutomirski <luto@amacapital.net>
Newsgroups linux.kernel
Subject Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core)
Date 2016-06-24 19:50 +0200
Message-ID <rNDoS-2OX-27@gated-at.bofh.it> (permalink)
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On Fri, Jun 24, 2016 at 10:40 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Fri, Jun 24, 2016 at 10:21 AM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>>
>> But as mentioned, I must have missed something. There were a number of
>> places where the code used the task_stack_page() and
>> task_thread_info() interchangably, which used to work and is no longer
>> true. There might simply be cases I missed.
>
> .. and immediately as I wrote that, I went "Duh".
>
> One place I missed was free_thread_info(), which should now free the
> stack, not the ti pointer. But it does
>
>         struct page *page = virt_to_page(ti);
>
> and frees that, which is bogus. It turns out that we do do
>
>         free_thread_info(tsk->stack);
>
> which is bogus too, and undoes it, but I think I have a few new places
> to look at..

Try patching in this thing, which cleans up a bunch of that core crap:

https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=x86/vmap_stack&id=7ca9fb6bbf2838cc94b2af41e94854d02649c58c

It might not apply without the rest of my series, though.

FWIW, your patch is much more lenient than my approach: I was planning
prohibiting architectures from supplying their own struct thread_info
if they put it in task_struct.  To make that work, I have patches to
remove everything but cpu, flags, and task from x86's thread_info
first.  I'm planning on tidying them up and sending them out after the
vmap stack stuff lands in -tip -- I don't want to have big series that
depend on each other flying around by email at the same time, because
everyone will go nuts trying to figure out what applies where.

--Andy

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Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-23 19:50 +0200
  Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-23 20:00 +0200
    Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Kees Cook <keescook@chromium.org> - 2016-06-23 20:10 +0200
      Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Peter Zijlstra <peterz@infradead.org> - 2016-06-23 21:00 +0200
    Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Oleg Nesterov <oleg@redhat.com> - 2016-06-23 20:20 +0200
      Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Peter Zijlstra <peterz@infradead.org> - 2016-06-23 21:00 +0200
    Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-23 20:50 +0200
      Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-23 21:10 +0200
    Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Peter Zijlstra <peterz@infradead.org> - 2016-06-23 21:00 +0200
      Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-23 21:20 +0200
        Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-24 08:20 +0200
          Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Brian Gerst <brgerst@gmail.com> - 2016-06-24 14:30 +0200
            Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-24 19:30 +0200
              Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-24 19:50 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-24 19:50 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-24 20:00 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-24 20:40 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-24 20:00 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-24 20:20 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-24 23:00 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Josh Poimboeuf <jpoimboe@redhat.com> - 2016-06-24 23:00 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-24 23:10 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-24 23:30 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-24 23:40 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-24 23:40 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-25 04:50 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-26 01:30 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-26 01:40 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-26 03:30 +0200
                Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Josh Poimboeuf <jpoimboe@redhat.com> - 2016-06-24 23:10 +0200
      Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski <luto@amacapital.net> - 2016-06-23 21:20 +0200
        Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Peter Zijlstra <peterz@infradead.org> - 2016-06-23 21:20 +0200
  Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Oleg Nesterov <oleg@redhat.com> - 2016-06-23 21:00 +0200
    Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Michal Hocko <mhocko@kernel.org> - 2016-06-24 16:20 +0200
      Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Michal Hocko <mhocko@kernel.org> - 2016-06-24 17:10 +0200
        Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages  (x86, core) Oleg Nesterov <oleg@redhat.com> - 2016-06-24 22:30 +0200
          Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,  core) Michal Hocko <mhocko@kernel.org> - 2016-06-27 12:40 +0200

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