From: Oleg Nesterov <oleg@redhat.com>
Date: Wed, 17 Jun 2009 23:27:31 +0000 (-0700)
Subject: ptrace: ptrace_attach: check PF_KTHREAD + exit_state instead of ->mm
X-Git-Tag: v2.6.31-rc1~220
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b79b7ba93df14a1fc0b8d4d6d78a0e097de03bbd;p=pandora-kernel.git

ptrace: ptrace_attach: check PF_KTHREAD + exit_state instead of ->mm

- Add PF_KTHREAD check to prevent attaching to the kernel thread
  with a borrowed ->mm.

  With or without this change we can race with daemonize() which
  can set PF_KTHREAD or clear ->mm after ptrace_attach() does the
  check, but this doesn't matter because reparent_to_kthreadd()
  does ptrace_unlink().

- Kill "!task->mm" check. We don't really care about ->mm != NULL,
  and the task can call exit_mm() right after we drop task_lock().
  What we need is to make sure we can't attach after exit_notify(),
  check task->exit_state != 0 instead.

Also, move the "already traced" check down for cosmetic reasons.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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