[PATCH] fix zap_thread's ptrace related problems

1. The tracee can go from ptrace_stop() to do_signal_stop()
   after __ptrace_unlink(p).

2. It is unsafe to __ptrace_unlink(p) while p->parent may wait
   for tasklist_lock in ptrace_detach().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 055378d2513e..0e1c95074d42 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1403,7 +1403,7 @@ static void zap_threads (struct mm_struct *mm)
                 do_each_thread(g,p) {
                         if (mm == p->mm && p != tsk &&
                             p->ptrace && p->parent->mm == mm) {
-                                __ptrace_unlink(p);
+                                __ptrace_detach(p, 0);
                         }
                 } while_each_thread(g,p);
                 write_unlock_irq(&tasklist_lock);