Groups > linux.kernel > #1619139

Re: scope of cred_guard_mutex.

From	Kees Cook <keescook@chromium.org>
Newsgroups	linux.kernel
Subject	Re: scope of cred_guard_mutex.
Date	2017-04-08 00:10 +0200
Message-ID	<ttKeS-59B-9@gated-at.bofh.it> (permalink)
References	(6 earlier) <trQop-2Lx-1@gated-at.bofh.it> <trV4J-5Uv-1@gated-at.bofh.it> <tsf3s-24M-23@gated-at.bofh.it> <tsj74-4Hf-5@gated-at.bofh.it> <tthZh-2Gn-23@gated-at.bofh.it>
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On Thu, Apr 6, 2017 at 8:55 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> And this makes me think again that we need to restart this discusion with
> more CC's.

I'm a fan of that; I've not been able to follow this thread as it
seems to have gone far from the original deadlock problem. :) I've
seen issues with ptrace, zombies, and now exec. I'm lost. :P

>> Partly I object because your understanding and my understanding of
>> cred_guard_mutex are very different.
>>
>> As I read and understand the code the job of cred_guard_mutex is to keep
>> ptrace (and other threads of the proccess) from interferring in
>> exec and to ensure old resources are accessed with permission checks
>> using our original credentials and that new and modified resources are
>> accessed with permission checks using our new credentials.
>
> Yes, this is clear.

Maybe stupid idea: can we get a patch that just adds this kind of
documentation somewhere in the source? If we can agree on the purpose
of cred_guard_mutex, and get it into the code, that seems like a good
step in discussion...

-Kees

-- 
Kees Cook
Pixel Security

Thread

Re: [RFC][PATCH] exec: Don't wait for ptraced threads to be reaped. ebiederm@xmission.com (Eric W. Biederman) - 2017-03-30 10:20 +0200
  [RFC][PATCH 0/2] exec: Fixing ptrace'd mulit-threaded hang ebiederm@xmission.com (Eric W. Biederman) - 2017-04-01 07:20 +0200
    [RFC][PATCH 1/2] sighand: Count each thread group once in sighand_struct ebiederm@xmission.com (Eric W. Biederman) - 2017-04-01 07:20 +0200
    [RFC][PATCH 2/2] exec: If possible don't wait for ptraced threads to be reaped ebiederm@xmission.com (Eric W. Biederman) - 2017-04-01 07:30 +0200
      Re: [RFC][PATCH 2/2] exec: If possible don't wait for ptraced  threads to be reaped Oleg Nesterov <oleg@redhat.com> - 2017-04-02 17:40 +0200
        Re: [RFC][PATCH 2/2] exec: If possible don't wait for ptraced threads to be reaped ebiederm@xmission.com (Eric W. Biederman) - 2017-04-02 21:00 +0200
          Re: [RFC][PATCH 2/2] exec: If possible don't wait for ptraced  threads to be reaped Oleg Nesterov <oleg@redhat.com> - 2017-04-03 20:20 +0200
            Re: [RFC][PATCH 2/2] exec: If possible don't wait for ptraced threads to be reaped ebiederm@xmission.com (Eric W. Biederman) - 2017-04-03 23:20 +0200
              Re: [RFC][PATCH 2/2] exec: If possible don't wait for ptraced         threads to be reaped Oleg Nesterov <oleg@redhat.com> - 2017-04-05 18:50 +0200
    Re: [RFC][PATCH 0/2] exec: Fixing ptrace'd mulit-threaded hang Oleg Nesterov <oleg@redhat.com> - 2017-04-02 17:40 +0200
    [RFC][PATCH v2 4/5] exec: If possible don't wait for ptraced threads to be reaped ebiederm@xmission.com (Eric W. Biederman) - 2017-04-03 01:00 +0200
      Re: [RFC][PATCH v2 4/5] exec: If possible don't wait for ptraced         threads to be reaped Oleg Nesterov <oleg@redhat.com> - 2017-04-05 18:20 +0200
    [RFC][PATCH v2 1/5] ptrace: Don't wait in PTRACE_O_TRACEEXIT for exec or coredump ebiederm@xmission.com (Eric W. Biederman) - 2017-04-03 01:00 +0200
      Re: [RFC][PATCH v2 1/5] ptrace: Don't wait in PTRACE_O_TRACEEXIT         for exec or coredump Oleg Nesterov <oleg@redhat.com> - 2017-04-05 18:30 +0200
    [RFC][PATCH v2 0/5] exec: Fixing ptrace'd mulit-threaded hang ebiederm@xmission.com (Eric W. Biederman) - 2017-04-03 01:00 +0200
      [RFC][PATCH v2 3/5] clone: Disallown CLONE_THREAD with a shared sighand_struct ebiederm@xmission.com (Eric W. Biederman) - 2017-04-03 01:00 +0200
        Re: [RFC][PATCH v2 3/5] clone: Disallown CLONE_THREAD with a         shared sighand_struct Oleg Nesterov <oleg@redhat.com> - 2017-04-05 18:30 +0200
          Re: [RFC][PATCH v2 3/5] clone: Disallown CLONE_THREAD with a shared sighand_struct ebiederm@xmission.com (Eric W. Biederman) - 2017-04-05 19:50 +0200
            Re: [RFC][PATCH v2 3/5] clone: Disallown CLONE_THREAD with a         shared sighand_struct Oleg Nesterov <oleg@redhat.com> - 2017-04-05 20:20 +0200
      [RFC][PATCH v2 2/5] sighand: Count each thread group once in sighand_struct ebiederm@xmission.com (Eric W. Biederman) - 2017-04-03 01:00 +0200
      [RFC][PATCH v2 5/5] signal: Don't allow accessing signal_struct by old threads after exec ebiederm@xmission.com (Eric W. Biederman) - 2017-04-03 01:10 +0200
        Re: [RFC][PATCH v2 5/5] signal: Don't allow accessing         signal_struct by old threads after exec Oleg Nesterov <oleg@redhat.com> - 2017-04-05 18:20 +0200
          Re: [RFC][PATCH v2 5/5] signal: Don't allow accessing signal_struct by old threads after exec ebiederm@xmission.com (Eric W. Biederman) - 2017-04-05 20:30 +0200
            Re: [RFC][PATCH v2 5/5] signal: Don't allow accessing signal_struct  by old threads after exec Oleg Nesterov <oleg@redhat.com> - 2017-04-06 18:00 +0200
  Re: [RFC][PATCH] exec: Don't wait for ptraced threads to be reaped. Oleg Nesterov <oleg@redhat.com> - 2017-04-02 18:20 +0200
    Re: [RFC][PATCH] exec: Don't wait for ptraced threads to be reaped. ebiederm@xmission.com (Eric W. Biederman) - 2017-04-02 23:20 +0200
      Re: [RFC][PATCH] exec: Don't wait for ptraced threads to be reaped. Oleg Nesterov <oleg@redhat.com> - 2017-04-03 20:40 +0200
        scope of cred_guard_mutex. ebiederm@xmission.com (Eric W. Biederman) - 2017-04-04 01:00 +0200
          Re: scope of cred_guard_mutex. Oleg Nesterov <oleg@redhat.com> - 2017-04-05 18:10 +0200
            Re: scope of cred_guard_mutex. Kees Cook <keescook@chromium.org> - 2017-04-05 18:20 +0200
            Re: scope of cred_guard_mutex. ebiederm@xmission.com (Eric W. Biederman) - 2017-04-05 20:10 +0200
              Re: scope of cred_guard_mutex. Oleg Nesterov <oleg@redhat.com> - 2017-04-05 20:20 +0200
          Re: scope of cred_guard_mutex. Oleg Nesterov <oleg@redhat.com> - 2017-04-06 18:00 +0200
            Re: scope of cred_guard_mutex. Kees Cook <keescook@chromium.org> - 2017-04-08 00:10 +0200
        Re: [RFC][PATCH] exec: Don't wait for ptraced threads to be reaped. ebiederm@xmission.com (Eric W. Biederman) - 2017-04-04 01:00 +0200

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