From 1904be1b6bb92058c8e00063dd59df2df294e258 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Tue, 20 Oct 2015 21:48:02 -0400 Subject: [PATCH] tracing: Do not allow stack_tracer to record stack in NMI The code in stack tracer should not be executed within an NMI as it grabs spinlocks and stack tracing an NMI gives the possibility of causing a deadlock. Although this is safe on x86_64, because it does not perform stack traces when the task struct stack is not in use (interrupts and NMIs), it may be an issue for NMIs on i386 and other archs that use the same stack as the NMI. Signed-off-by: Steven Rostedt --- kernel/trace/trace_stack.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index 5f29402..8abf1ba 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -85,6 +85,10 @@ check_stack(unsigned long ip, unsigned long *stack) if (!object_is_on_stack(stack)) return; + /* Can't do this from NMI context (can cause deadlocks) */ + if (in_nmi()) + return; + local_irq_save(flags); arch_spin_lock(&max_stack_lock); -- 2.7.4