2 files changed, 13 insertions, 2 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ebff62ef40be..20e066065eb3 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2739,15 +2739,20 @@ void unregister_ftrace_graph(void)
 void ftrace_graph_init_task(struct task_struct *t)
 {
         if (atomic_read(&ftrace_graph_active)) {
-                t->ret_stack = kmalloc(FTRACE_RETFUNC_DEPTH
+                struct ftrace_ret_stack *ret_stack;
+
+                ret_stack = kmalloc(FTRACE_RETFUNC_DEPTH
                                 * sizeof(struct ftrace_ret_stack),
                                 GFP_KERNEL);
-                if (!t->ret_stack)
+                if (!ret_stack)
                         return;
                 t->curr_ret_stack = -1;
                 atomic_set(&t->tracing_graph_pause, 0);
                 atomic_set(&t->trace_overrun, 0);
                 t->ftrace_timestamp = 0;
+                /* make curr_ret_stack visable before we add the ret_stack */
+                smp_wmb();
+                t->ret_stack = ret_stack;
         } else
                 t->ret_stack = NULL;
 }
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index d28687e7b3a7..baeb5fe36108 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -65,6 +65,12 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth)
         if (!current->ret_stack)
                 return -EBUSY;
 
+        /*
+         * We must make sure the ret_stack is tested before we read
+         * anything else.
+         */
+        smp_rmb();
+
         /* The return trace stack is full */
         if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) {
                 atomic_inc(&current->trace_overrun);