Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read.

From	Andy Lutomirski <luto@amacapital.net>
Newsgroups	linux.kernel
Subject	Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read.
Date	2016-10-19 17:40 +0200
Message-ID	<su18e-37s-49@gated-at.bofh.it> (permalink)
References	(3 earlier) <stEbE-3pl-37@gated-at.bofh.it> <stEEF-3BE-29@gated-at.bofh.it> <stI5z-6a9-9@gated-at.bofh.it> <stJO2-7sS-41@gated-at.bofh.it> <stJXI-7yE-13@gated-at.bofh.it>
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On Tue, Oct 18, 2016 at 2:15 PM, Eric W. Biederman
<ebiederm@xmission.com> wrote:
>
> When the user namespace support was merged the need to prevent
> ptracing an executable that is not readable was overlooked.

Before getting too excited about this fix, isn't there a much bigger
hole that's been there forever?  Simply ptrace yourself, exec the
program, and then dump the program out.  A program that really wants
to be unreadable should have a stub: the stub is setuid and readable,
but all the stub does is to exec the real program, and the real
program should have mode 0500 or similar.

ISTM the "right" check would be to enforce that the program's new
creds can read the program, but that will break backwards
compatibility.

--Andy

Thread

Re: [REVIEW][PATCH] mm: Add a user_ns owner to mm_struct and fix  ptrace_may_access Michal Hocko <mhocko@kernel.org> - 2016-10-18 16:00 +0200
  Re: [REVIEW][PATCH] mm: Add a user_ns owner to mm_struct and fix  ptrace_may_access Jann Horn <jann@thejh.net> - 2016-10-18 16:00 +0200
  Re: [REVIEW][PATCH] mm: Add a user_ns owner to mm_struct and fix ptrace_may_access ebiederm@xmission.com (Eric W. Biederman) - 2016-10-18 17:00 +0200
    Re: [REVIEW][PATCH] mm: Add a user_ns owner to mm_struct and fix  ptrace_may_access Jann Horn <jann@thejh.net> - 2016-10-18 17:10 +0200
      Re: [REVIEW][PATCH] mm: Add a user_ns owner to mm_struct and fix ptrace_may_access ebiederm@xmission.com (Eric W. Biederman) - 2016-10-18 17:40 +0200
        Re: [REVIEW][PATCH] mm: Add a user_ns owner to mm_struct and fix  ptrace_may_access Jann Horn <jann@thejh.net> - 2016-10-18 21:20 +0200
          Re: [REVIEW][PATCH] mm: Add a user_ns owner to mm_struct and fix ptrace_may_access ebiederm@xmission.com (Eric W. Biederman) - 2016-10-18 23:10 +0200
            [REVIEW][PATCH] exec: Don't exec files the userns root can not read. ebiederm@xmission.com (Eric W. Biederman) - 2016-10-18 23:20 +0200
              Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read. Amir Goldstein <amir73il@gmail.com> - 2016-10-19 08:20 +0200
                Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read. ebiederm@xmission.com (Eric W. Biederman) - 2016-10-19 17:10 +0200
                Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read. ebiederm@xmission.com (Eric W. Biederman) - 2016-10-19 19:10 +0200
              Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read. Andy Lutomirski <luto@amacapital.net> - 2016-10-19 17:40 +0200
                Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read. ebiederm@xmission.com (Eric W. Biederman) - 2016-10-19 19:00 +0200
                Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not  read. Jann Horn <jann@thejh.net> - 2016-10-19 19:30 +0200
                Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read. Andy Lutomirski <luto@amacapital.net> - 2016-10-19 19:40 +0200
                Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read. ebiederm@xmission.com (Eric W. Biederman) - 2016-10-19 20:00 +0200
                Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read. Andy Lutomirski <luto@amacapital.net> - 2016-10-19 20:40 +0200
                Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read. ebiederm@xmission.com (Eric W. Biederman) - 2016-10-19 23:30 +0200
                Re: [REVIEW][PATCH] exec: Don't exec files the userns root can not read. Andy Lutomirski <luto@amacapital.net> - 2016-10-20 01:20 +0200
    Re: [REVIEW][PATCH] mm: Add a user_ns owner to mm_struct and fix  ptrace_may_access Michal Hocko <mhocko@kernel.org> - 2016-10-18 20:10 +0200

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