linux-kernel - [PATCH 0/8] make vfork killable/restartable/traceable

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Date:	Wed, 27 Jul 2011 18:31:59 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Roland McGrath <roland@...k.frob.com>,
	Tejun Heo <tj@...nel.org>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Matt Fleming <matt.fleming@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 0/8] make vfork killable/restartable/traceable

Hello.

CLONE_VFORK sleeps in TASK_INTERRUPTIBLE until the child exits/execs.
This is obviously not good, it is sooo simple to create the task which
doesn't react to SIGKILL/SIGSTOP.

Questions:

	- do we really need this?

	  I think we do. This really "looks like a bug" in any case,
	  even if nobody ever complained afaik.

	- may be 1-3 is enough?

	  may be... but personally I think SIGSTOP/ptrace should work
	  too.

	- is it safe to exit/stop on !x86 machine???

	  I do not know. May be this needs some #ifdef's around
	  wait_for_completion_interruptible(). I am not sure that,
	  say, arch_ptrace_stop() can't abuse the ->mm shared with
	  the child.

	  OTOH. This can happen anyway, do_fork() does ptrace_event()
	  before wait_for_completion().

	- and of course, while I think this is bugfix, this is user
	  visible change.

Please comment.

9/8 is off-topic.

Oleg.

 fs/exec.c                   |   11 ----
 include/linux/sched.h       |    2 +-
 include/linux/thread_info.h |    4 ++
 kernel/fork.c               |  121 ++++++++++++++++++++++++++++++++++---------
 kernel/pid.c                |   13 +++++
 5 files changed, 114 insertions(+), 37 deletions(-)

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