linux-kernel - [RFC][PATCH v2 0/5] exec: Fixing ptrace'd mulit-threaded hang

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Date:   Sun, 02 Apr 2017 17:50:02 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Aleksa Sarai <asarai@...e.com>,
        Andy Lutomirski <luto@...capital.net>,
        Attila Fazekas <afazekas@...hat.com>,
        Jann Horn <jann@...jh.net>, Kees Cook <keescook@...omium.org>,
        Michal Hocko <mhocko@...nel.org>,
        Ulrich Obergfell <uobergfe@...hat.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org
Subject: [RFC][PATCH v2 0/5] exec: Fixing ptrace'd mulit-threaded hang


Oleg your comment about kill being able to send signal was an important
dimension I had missed thank you.

This patchset just denies the case of SIGHAND between different
multi-threaded processes as I don't think anyone cares.  I can
fix that if anyone cares but I am not certain we actally do.

I have reworked the ptrace notification code so that we always
send notifications if we can but don't wait if it is a coredump
or an exec.  Which simpilifies the code nicely.

A few more tweaks are needed before a final version but I think
things are compelling.

 fs/exec.c                    |  23 ++-------
 include/linux/sched/signal.h |   1 +
 kernel/exit.c                |  20 ++++----
 kernel/fork.c                |  14 +++++-
 kernel/ptrace.c              |   4 ++
 kernel/signal.c              | 112 +++++++++++++++++++------------------------
 6 files changed, 78 insertions(+), 96 deletions(-)

Eric W. Biederman (5):
      ptrace: Don't wait in PTRACE_O_TRACEEXIT for exec or coredump
      sighand: Count each thread group once in sighand_struct
      clone: Disallown CLONE_THREAD with a shared sighand_struct
      exec: If possible don't wait for ptraced threads to be reaped
      signal: Don't allow accessing signal_struct by old threads after exec

Eric