3.10.76 -> 3.10.77

1 files changed, 20 insertions, 0 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index afadcf7b4..118323bc8 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -720,6 +720,8 @@ static int ptrace_peek_siginfo(struct task_struct *child,
 static int ptrace_resume(struct task_struct *child, long request,
 			 unsigned long data)
 {
+	bool need_siglock;
+
 	if (!valid_signal(data))
 		return -EIO;
 
@@ -747,8 +749,26 @@ static int ptrace_resume(struct task_struct *child, long request,
 		user_disable_single_step(child);
 	}
 
+	/*
+	 * Change ->exit_code and ->state under siglock to avoid the race
+	 * with wait_task_stopped() in between; a non-zero ->exit_code will
+	 * wrongly look like another report from tracee.
+	 *
+	 * Note that we need siglock even if ->exit_code == data and/or this
+	 * status was not reported yet, the new status must not be cleared by
+	 * wait_task_stopped() after resume.
+	 *
+	 * If data == 0 we do not care if wait_task_stopped() reports the old
+	 * status and clears the code too; this can't race with the tracee, it
+	 * takes siglock after resume.
+	 */
+	need_siglock = data && !thread_group_empty(current);
+	if (need_siglock)
+		spin_lock_irq(&child->sighand->siglock);
 	child->exit_code = data;
 	wake_up_state(child, __TASK_TRACED);
+	if (need_siglock)
+		spin_unlock_irq(&child->sighand->siglock);
 
 	return 0;
 }