linux-kernel - [PATCH 0/2] exec: Fix dead-lock in de_thread with ptrace

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Message-ID: <AM6PR03MB5170396D87DED49FE00BC624E4FB0@AM6PR03MB5170.eurprd03.prod.outlook.com>
Date:   Sat, 14 Mar 2020 10:12:43 +0100
From:   Bernd Edlinger <bernd.edlinger@...mail.de>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Christian Brauner <christian.brauner@...ntu.com>,
        Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Oleg Nesterov <oleg@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Andrei Vagin <avagin@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Yuyang Du <duyuyang@...il.com>,
        David Hildenbrand <david@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Anshuman Khandual <anshuman.khandual@....com>,
        David Howells <dhowells@...hat.com>,
        James Morris <jamorris@...ux.microsoft.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christian Kellner <christian@...lner.me>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Aleksa Sarai <cyphar@...har.com>,
        "Dmitry V. Levin" <ldv@...linux.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>
Subject: [PATCH 0/2] exec: Fix dead-lock in de_thread with ptrace_attach

This completes the new infrastructure patch, and replaces the
cred_guard_mutex with an exec_guard_mutex, and a boolean, that
is set, when a dead-lock situation is detected.

I also change ptrace_traceme to use the new mutex, but I consider
it a bug, that it didn't take any mutex previously since it calls
security_ptrace_traceme, and all the security modules operate under
the assumption that execve is not operating in parallel.

This patch fixes the test case tools/testing/selftests/ptrace/vmaccess:

[==========] Running 2 tests from 1 test cases.
[ RUN      ] global.vmaccess
[       OK ] global.vmaccess
[ RUN      ] global.attach
[       OK ] global.attach  <= this was still failing
[==========] 2 / 2 tests passed.
[  PASSED  ]

Yes, it is an API change, but only in some very special case,
so I would exepect this to be un-noticeable to user space applications.

Bernd Edlinger (2):
  exec: Fix dead-lock in de_thread with ptrace_attach
  doc: Update documentation of ->exec_*_mutex

 Documentation/security/credentials.rst | 29 +++++++++++++++-------
 fs/exec.c                              | 44 +++++++++++++++++++++++++++-------
 fs/proc/base.c                         | 13 ++++++----
 include/linux/sched/signal.h           | 14 +++++++----
 init/init_task.c                       |  2 +-
 kernel/cred.c                          |  2 +-
 kernel/fork.c                          |  2 +-
 kernel/ptrace.c                        | 20 +++++++++++++---
 kernel/seccomp.c                       | 15 +++++++-----
 9 files changed, 102 insertions(+), 39 deletions(-)

-- 
1.9.1