Commit ea14eb71 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
Browse files

function-graph: Init curr_ret_stack with ret_stack

If the graph tracer is active, and a task is forked but the allocating of
the processes graph stack fails, it can cause crash later on.

This is due to the temporary stack being NULL, but the curr_ret_stack
variable is copied from the parent. If it is not -1, then in
ftrace_graph_probe_sched_switch() the following:

	for (index = next->curr_ret_stack; index >= 0; index--)
		next->ret_stack[index].calltime += timestamp;

Will cause a kernel OOPS.

Found with Li Zefan's ftrace_stress_test.

Signed-off-by: default avatarSteven Rostedt <>
parent 52fbe9cd
......@@ -3349,6 +3349,7 @@ void ftrace_graph_init_task(struct task_struct *t)
/* Make sure we do not use the parent ret_stack */
t->ret_stack = NULL;
t->curr_ret_stack = -1;
if (ftrace_graph_active) {
struct ftrace_ret_stack *ret_stack;
......@@ -3358,7 +3359,6 @@ void ftrace_graph_init_task(struct task_struct *t)
if (!ret_stack)
t->curr_ret_stack = -1;
atomic_set(&t->tracing_graph_pause, 0);
atomic_set(&t->trace_overrun, 0);
t->ftrace_timestamp = 0;
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