From: Steven Rostedt Date: Tue, 2 Jun 2009 18:01:19 +0000 (-0400) Subject: function-graph: add memory barriers for accessing task's ret_stack X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=26c01624a2a40f8a4ddf6449b65c9b1c418d0e72;p=linux-beck.git function-graph: add memory barriers for accessing task's ret_stack The code that handles the tasks ret_stack allocation for every task assumes that only an interrupt can cause issues (even though interrupts are disabled). In reality, the code is allocating the ret_stack for tasks that may be running on other CPUs and there are not efficient memory barriers to handle this case. [ Impact: prevent crash due to using of uninitialized ret_stack variables ] Signed-off-by: Steven Rostedt --- diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 20e066065eb3..1664d3f33d38 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2580,12 +2580,12 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list) } if (t->ret_stack == NULL) { - t->curr_ret_stack = -1; - /* Make sure IRQs see the -1 first: */ - barrier(); - t->ret_stack = ret_stack_list[start++]; atomic_set(&t->tracing_graph_pause, 0); atomic_set(&t->trace_overrun, 0); + t->curr_ret_stack = -1; + /* Make sure the tasks see the -1 first: */ + smp_wmb(); + t->ret_stack = ret_stack_list[start++]; } } while_each_thread(g, t);