Merge v7.1.5linux-rolling-stable

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 9c2b32c4d755..bbc0fd4cc4d7 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1362,8 +1362,16 @@ struct sighand_struct *lock_task_sighand(struct task_struct *tsk,
 	rcu_read_lock();
 	for (;;) {
 		sighand = rcu_dereference(tsk->sighand);
-		if (unlikely(sighand == NULL))
+		if (unlikely(sighand == NULL)) {
+			/*
+			 * Pairs with the smp_store_release() in
+			 * __exit_signal().  It ensures that all state
+			 * modifications to the task preceeding the store are
+			 * visible to the callers of lock_task_sighand().
+			 */
+			smp_acquire__after_ctrl_dep();
 			break;
+		}
 
 		/*
 		 * This sighand can be already freed and even reused, but