Re: next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0

From	Andy Lutomirski <luto@kernel.org>
Newsgroups	linux.kernel
Subject	Re: next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0
Date	2017-05-19 21:20 +0200
Message-ID	<tIVBp-6Cu-27@gated-at.bofh.it> (permalink)
References	(8 earlier) <tIGsF-4nn-3@gated-at.bofh.it> <tISka-4bg-39@gated-at.bofh.it> <tIU2B-5nJ-13@gated-at.bofh.it> <tIUOZ-5Wm-1@gated-at.bofh.it> <tIVBo-6Cu-13@gated-at.bofh.it>
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On Fri, May 19, 2017 at 12:16 PM, Kees Cook <keescook@chromium.org> wrote:
> On Fri, May 19, 2017 at 11:27 AM, Andy Lutomirski <luto@kernel.org> wrote:
>> One thing I've pondered: can we make some debugging mode (kmemleak,
>> perhaps?) check that freed memory is RW at the time it's freed?  I
>> once wrote some buggy code that freed an R page and caused an OOPS
>> much later, and this bug here seems likely to be some code that frees
>> RWX memory.
>
> Which begs for even more checks: nothing should ever make a page RWX.
> Either R, RW, or RX only... (or X too I guess, in the future).

I could see pages being RWX temporarily during boot.  OTOH if we ban
RWX outright (after very early boot, anyway), then catching code that
messes up and leaves pages RWX gets much easier.

--Andy

Thread

next-20170515: WARNING: CPU: 0 PID: 1 at  arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0 "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-16 00:10 +0200
  Re: next-20170515: WARNING: CPU: 0 PID: 1 at  arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0 "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-16 00:20 +0200
    Re: next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236  note_page+0x630/0x7e0 Kees Cook <keescook@chromium.org> - 2017-05-16 01:00 +0200
      Re: next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236  note_page+0x630/0x7e0 "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-16 01:50 +0200
        Re: next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236  note_page+0x630/0x7e0 Kees Cook <keescook@chromium.org> - 2017-05-16 02:20 +0200
          Re: next-20170515: WARNING: CPU: 0 PID: 1 at  arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0 "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-17 18:50 +0200
            Re: next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236  note_page+0x630/0x7e0 Kees Cook <keescook@chromium.org> - 2017-05-17 20:00 +0200
              Re: next-20170515: WARNING: CPU: 0 PID: 1 at  arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0 "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-19 02:50 +0200
                Re: next-20170515: WARNING: CPU: 0 PID: 1 at  arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0 "Luis R. Rodriguez" <mcgrof@kenrel.org> - 2017-05-19 05:10 +0200
                Re: next-20170515: WARNING: CPU: 0 PID: 1 at  arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0 "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-19 17:50 +0200
                Re: next-20170515: WARNING: CPU: 0 PID: 1 at  arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0 "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-19 19:30 +0200
                Re: next-20170515: WARNING: CPU: 0 PID: 1 at  arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0 Masami Hiramatsu <mhiramat@kernel.org> - 2017-05-20 04:40 +0200
                Re: next-20170515: WARNING: CPU: 0 PID: 1 at  arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0 "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-23 16:50 +0200
                Re: next-20170515: WARNING: CPU: 0 PID: 1 at  arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0 "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-24 20:00 +0200
                Re: next-20170515: WARNING: CPU: 0 PID: 1 at  arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0 Catalin Marinas <catalin.marinas@arm.com> - 2017-05-19 19:40 +0200
                Re: next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236  note_page+0x630/0x7e0 Andy Lutomirski <luto@kernel.org> - 2017-05-19 20:30 +0200
                Re: next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236  note_page+0x630/0x7e0 Kees Cook <keescook@chromium.org> - 2017-05-19 21:20 +0200
                Re: next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236  note_page+0x630/0x7e0 Andy Lutomirski <luto@kernel.org> - 2017-05-19 21:20 +0200
                Re: next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236  note_page+0x630/0x7e0 Kees Cook <keescook@chromium.org> - 2017-05-19 21:30 +0200
    Re: next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236  note_page+0x630/0x7e0 "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-16 01:40 +0200

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