Merge remote-tracking branch 'torvalds/master' into perf/core

To pick up fixes from perf/urgent.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 17 insertions, 1 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 76f09456ec4b..2997ca600d18 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -170,6 +170,21 @@ void __ptrace_unlink(struct task_struct *child)
 	spin_unlock(&child->sighand->siglock);
 }
 
+static bool looks_like_a_spurious_pid(struct task_struct *task)
+{
+	if (task->exit_code != ((PTRACE_EVENT_EXEC << 8) | SIGTRAP))
+		return false;
+
+	if (task_pid_vnr(task) == task->ptrace_message)
+		return false;
+	/*
+	 * The tracee changed its pid but the PTRACE_EVENT_EXEC event
+	 * was not wait()'ed, most probably debugger targets the old
+	 * leader which was destroyed in de_thread().
+	 */
+	return true;
+}
+
 /* Ensure that nothing can wake it up, even SIGKILL */
 static bool ptrace_freeze_traced(struct task_struct *task)
 {
@@ -180,7 +195,8 @@ static bool ptrace_freeze_traced(struct task_struct *task)
 		return ret;
 
 	spin_lock_irq(&task->sighand->siglock);
-	if (task_is_traced(task) && !__fatal_signal_pending(task)) {
+	if (task_is_traced(task) && !looks_like_a_spurious_pid(task) &&
+	    !__fatal_signal_pending(task)) {
 		task->state = __TASK_TRACED;
 		ret = true;
 	}