1 files changed, 18 insertions, 1 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 0291a68a3626..3234a0c32d54 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -678,6 +678,18 @@ static int de_thread(struct task_struct *tsk)
                 while (leader->exit_state != EXIT_ZOMBIE)
                         yield();
 
+                /*
+                 * The only record we have of the real-time age of a
+                 * process, regardless of execs it's done, is start_time.
+                 * All the past CPU time is accumulated in signal_struct
+                 * from sister threads now dead.  But in this non-leader
+                 * exec, nothing survives from the original leader thread,
+                 * whose birth marks the true age of this process now.
+                 * When we take on its identity by switching to its PID, we
+                 * also take its birthdate (always earlier than our own).
+                 */
+                current->start_time = leader->start_time;
+
                 spin_lock(&leader->proc_lock);
                 spin_lock(&current->proc_lock);
                 proc_dentry1 = proc_pid_unhash(current);
@@ -723,7 +735,12 @@ static int de_thread(struct task_struct *tsk)
                 current->parent = current->real_parent = leader->real_parent;
                 leader->parent = leader->real_parent = child_reaper;
                 current->group_leader = current;
-                leader->group_leader = leader;
+                leader->group_leader = current;
+
+                /* Reduce leader to a thread */
+                detach_pid(leader, PIDTYPE_PGID);
+                detach_pid(leader, PIDTYPE_SID);
+                list_del_init(&leader->tasks);
 
                 add_parent(current);
                 add_parent(leader);