Kill some obsolete sub-thread-ptrace stuff

There is a couple of subtle checks which were needed to handle ptracing from
the same thread group. This was deprecated a long ago, imho this code just
complicates the understanding.

And, the "->parent->signal->flags & SIGNAL_GROUP_EXIT" check in exit_notify()
is not right. SIGNAL_GROUP_EXIT can mean exec(), not exit_group(). This means
ptracer can lose a ptraced zombie on exec(). Minor problem, but still the bug.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 2 insertions, 10 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 464c2b172f07..9578c1ae19ca 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -813,7 +813,7 @@ static void exit_notify(struct task_struct *tsk)
                 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
         }
 
-        /* Let father know we died 
+        /* Let father know we died
          *
          * Thread signals are configurable, but you aren't going to use
          * that to send signals to arbitary processes. 
@@ -826,9 +826,7 @@ static void exit_notify(struct task_struct *tsk)
          * If our self_exec id doesn't match our parent_exec_id then
          * we have changed execution domain as these two values started
          * the same after a fork.
-         *      
          */
-        
         if (tsk->exit_signal != SIGCHLD && tsk->exit_signal != -1 &&
             ( tsk->parent_exec_id != t->self_exec_id  ||
               tsk->self_exec_id != tsk->parent_exec_id)
@@ -848,9 +846,7 @@ static void exit_notify(struct task_struct *tsk)
         }
 
         state = EXIT_ZOMBIE;
-        if (tsk->exit_signal == -1 &&
-            (likely(tsk->ptrace == 0) ||
-             unlikely(tsk->parent->signal->flags & SIGNAL_GROUP_EXIT)))
+        if (tsk->exit_signal == -1 && likely(!tsk->ptrace))
                 state = EXIT_DEAD;
         tsk->exit_state = state;
 
diff --git a/kernel/signal.c b/kernel/signal.c
index ef8156a6aad5..b27c01a66448 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1561,10 +1561,6 @@ static inline int may_ptrace_stop(void)
                     (current->ptrace & PT_ATTACHED)))
                 return 0;
 
-        if (unlikely(current->signal == current->parent->signal) &&
-            unlikely(current->signal->flags & SIGNAL_GROUP_EXIT))
-                return 0;
-
         /*
          * Are we in the middle of do_coredump?
          * If so and our tracer is also part of the coredump stopping