ptrace: tracehook_report_clone: fix false positives
authorOleg Nesterov <oleg@redhat.com>
Thu, 4 Jun 2009 23:29:07 +0000 (16:29 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 5 Jun 2009 01:07:40 +0000 (18:07 -0700)
commit087eb437051b3de817720f9c80c440fc9e7dcce8
tree25a72acabe05c3e72dddd942855d4245dfae4b82
parentb87297fb405ef13cac375f202d114323b076a56d
ptrace: tracehook_report_clone: fix false positives

The "trace || CLONE_PTRACE" check in tracehook_report_clone() is not right,

- If the untraced task does clone(CLONE_PTRACE) the new child is not traced,
  we must not queue SIGSTOP.

- If we forked the traced task, but the tracer exits and untraces both the
  forking task and the new child (after copy_process() drops tasklist_lock),
  we should not queue SIGSTOP too.

Change the code to check task_ptrace() != 0 instead. This is still racy, but
the race is harmless.

We can race with another tracer attaching to this child, or the tracer can
exit and detach in parallel. But giwen that we didn't do wake_up_new_task()
yet, the child must have the pending SIGSTOP anyway.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/tracehook.h
kernel/fork.c