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Re: [PATCH v5 2/4] x86/ldt: Make modify_ldt synchronous

From	Boris Ostrovsky <boris.ostrovsky@oracle.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v5 2/4] x86/ldt: Make modify_ldt synchronous
Date	2015-07-31 19:00 +0200
Message-ID	<pSlP5-3eU-13@gated-at.bofh.it> (permalink)
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On 07/30/2015 03:25 PM, Andy Lutomirski wrote:
> On Thu, Jul 30, 2015 at 11:35 AM, Boris Ostrovsky
> <boris.ostrovsky@oracle.com> wrote:
>> [OK]    LDT entry 0 has AR 0x0040F200 and limit 0x00000000
>> [OK]    LDT entry 0 is invalid
>> [RUN]   Cross-CPU LDT invalidation
>> Segmentation fault (core dumped)
> That's not good.
>
> Can you backtrace it?  (I.e. compite ldt_gdt_32 with -g and load the
> core dumb in gdb?)  My best guesses are either a signal delivery
> failure (although that shouldn't be a problem for 32-bit userspace on
> any kernel) or an actual LDT access fault, and the latter would be
> interesting.
>
> I haven't been able to reproduce this.

This looks like a userspace bug. Breaks on F18, works fine in F22.

Possibly something about signal handling --- I noticed on F18 I'd get 
two SEGV's in a row whereas we should only get one.

Anyway, this is not an issue as far as this thread is concerned.

-boris
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Thread

[PATCH v5 0/4] x86: modify_ldt improvement, test, and config option Andy Lutomirski <luto@kernel.org> - 2015-07-28 07:40 +0200
  [PATCH v5 2/4] x86/ldt: Make modify_ldt synchronous Andy Lutomirski <luto@kernel.org> - 2015-07-28 07:40 +0200
    Re: [PATCH v5 2/4] x86/ldt: Make modify_ldt synchronous Borislav Petkov <bp@alien8.de> - 2015-07-30 09:50 +0200
    Re: [PATCH v5 2/4] x86/ldt: Make modify_ldt synchronous Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-07-30 20:40 +0200
      Re: [PATCH v5 2/4] x86/ldt: Make modify_ldt synchronous Andy Lutomirski <luto@amacapital.net> - 2015-07-30 21:30 +0200
        Re: [PATCH v5 2/4] x86/ldt: Make modify_ldt synchronous Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-07-31 19:00 +0200
  [PATCH v5 3/4] selftests/x86, x86/ldt: Add a selftest for modify_ldt Andy Lutomirski <luto@kernel.org> - 2015-07-28 07:40 +0200
  [PATCH v5 4/4] x86/ldt: Make modify_ldt optional Andy Lutomirski <luto@kernel.org> - 2015-07-28 07:40 +0200
    Re: [PATCH v5 4/4] x86/ldt: Make modify_ldt optional Kees Cook <keescook@chromium.org> - 2015-07-28 22:50 +0200
      Re: [PATCH v5 4/4] x86/ldt: Make modify_ldt optional Willy Tarreau <w@1wt.eu> - 2015-07-28 23:00 +0200
  Re: [PATCH v5 0/4] x86: modify_ldt improvement, test, and config  option Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-07-30 18:00 +0200
    Re: [PATCH v5 0/4] x86: modify_ldt improvement, test, and config  option Borislav Petkov <bp@alien8.de> - 2015-07-30 18:10 +0200

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