tree a7cb72753c85cf79ac6fa31863d65d2f081e0823
parent 52fbe9cde7fdb5c6fac196d7ebd2d92d05ef3cd4
author Steven Rostedt <srostedt@redhat.com> 1268440883 -0500
committer Steven Rostedt <rostedt@goodmis.org> 1268443682 -0500

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.

Cc: stable@kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>