[PATCH 0/8] make vfork killable/restartable/traceable

[Oleg Nesterov <oleg@redhat.com>]

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(-)