[PATCH] coredump: kill ptrace related stuff

With this patch zap_process() sets SIGNAL_GROUP_EXIT while sending SIGKILL to
the thread group.  This means that a TASK_TRACED task

	1. Will be awakened by signal_wake_up(1)

	2. Can't sleep again via ptrace_notify()

	3. Can't go to do_signal_stop() after return
	   from ptrace_stop() in get_signal_to_deliver()

So we can remove all ptrace related stuff from coredump path.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 25 deletions

diff --git a/fs/exec.c b/fs/exec.c
index a5c51646d1ad..b58ba7d127e0 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1368,12 +1368,14 @@ static void format_corename(char *corename, const char *pattern, long signr)
         *out_ptr = 0;
 }
 
-static void zap_process(struct task_struct *start, int *ptraced)
+static void zap_process(struct task_struct *start)
 {
         struct task_struct *t;
         unsigned long flags;
 
         spin_lock_irqsave(&start->sighand->siglock, flags);
+        start->signal->flags = SIGNAL_GROUP_EXIT;
+        start->signal->group_stop_count = 0;
 
         t = start;
         do {
@@ -1381,22 +1383,17 @@ static void zap_process(struct task_struct *start, int *ptraced)
                         t->mm->core_waiters++;
                         sigaddset(&t->pending.signal, SIGKILL);
                         signal_wake_up(t, 1);
-
-                        if (unlikely(t->ptrace) &&
-                            unlikely(t->parent->mm == t->mm))
-                                *ptraced = 1;
                 }
         } while ((t = next_thread(t)) != start);
 
         spin_unlock_irqrestore(&start->sighand->siglock, flags);
 }
 
-static void zap_threads (struct mm_struct *mm)
+static void zap_threads(struct mm_struct *mm)
 {
         struct task_struct *g, *p;
         struct task_struct *tsk = current;
         struct completion *vfork_done = tsk->vfork_done;
-        int traced = 0;
 
         /*
          * Make sure nobody is waiting for us to release the VM,
@@ -1413,29 +1410,12 @@ static void zap_threads (struct mm_struct *mm)
                 do {
                         if (p->mm) {
                                 if (p->mm == mm)
-                                        zap_process(p, &traced);
+                                        zap_process(p);
                                 break;
                         }
                 } while ((p = next_thread(p)) != g);
         }
         read_unlock(&tasklist_lock);
-
-        if (unlikely(traced)) {
-                /*
-                 * We are zapping a thread and the thread it ptraces.
-                 * If the tracee went into a ptrace stop for exit tracing,
-                 * we could deadlock since the tracer is waiting for this
-                 * coredump to finish.  Detach them so they can both die.
-                 */
-                write_lock_irq(&tasklist_lock);
-                do_each_thread(g,p) {
-                        if (mm == p->mm && p != tsk &&
-                            p->ptrace && p->parent->mm == mm) {
-                                __ptrace_detach(p, 0);
-                        }
-                } while_each_thread(g,p);
-                write_unlock_irq(&tasklist_lock);
-        }
 }
 
 static void coredump_wait(struct mm_struct *mm)