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Message-ID: <20131114152304.GC5364@laptop.programming.kicks-ass.net>
Date: Thu, 14 Nov 2013 16:23:04 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Frederic Weisbecker <fweisbec@...il.com>
Cc: Vince Weaver <vincent.weaver@...ne.edu>,
Steven Rostedt <rostedt@...dmis.org>,
LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>, Dave Jones <davej@...hat.com>
Subject: Re: perf/tracepoint: another fuzzer generated lockup
On Sat, Nov 09, 2013 at 04:10:14PM +0100, Peter Zijlstra wrote:
> Cute.. so what appears to happen is that:
>
> 1) we trace irq_work_exit
> 2) we generate event
> 3) event needs to deliver signal
> 4) we queue irq_work to send signal
> 5) goto 1
---
arch/x86/include/asm/trace/irq_vectors.h | 11 +++++++++++
include/linux/ftrace_event.h | 16 ++++++++++++++++
include/linux/tracepoint.h | 4 ++++
include/trace/ftrace.h | 7 +++++++
kernel/trace/trace_event_perf.c | 6 ++++++
5 files changed, 44 insertions(+)
diff --git a/arch/x86/include/asm/trace/irq_vectors.h b/arch/x86/include/asm/trace/irq_vectors.h
index 2874df24e7a4..4cab890007a7 100644
--- a/arch/x86/include/asm/trace/irq_vectors.h
+++ b/arch/x86/include/asm/trace/irq_vectors.h
@@ -72,6 +72,17 @@ DEFINE_IRQ_VECTOR_EVENT(x86_platform_ipi);
DEFINE_IRQ_VECTOR_EVENT(irq_work);
/*
+ * We must dis-allow sampling irq_work_exit() because perf event sampling
+ * itself can cause irq_work, which would lead to an infinite loop;
+ *
+ * 1) irq_work_exit happens
+ * 2) generates perf sample
+ * 3) generates irq_work
+ * 4) goto 1
+ */
+TRACE_EVENT_PERF_PERM(irq_work_exit, is_sampling_event(p_event) ? -EPERM : 0);
+
+/*
* call_function - called when entering/exiting a call function interrupt
* vector handler
*/
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 5eaa746735ff..3e4d05566022 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -244,6 +244,9 @@ struct ftrace_event_call {
#ifdef CONFIG_PERF_EVENTS
int perf_refcount;
struct hlist_head __percpu *perf_events;
+
+ int (*perf_perm)(struct ftrace_event_call *,
+ struct perf_event *);
#endif
};
@@ -306,6 +309,19 @@ struct ftrace_event_file {
} \
early_initcall(trace_init_flags_##name);
+#define __TRACE_EVENT_PERF_PERM(name, expr) \
+ static int perf_perm_##name(struct ftrace_event_call *tp_event, \
+ struct perf_event *p_event) \
+ { \
+ return expr; \
+ } \
+ static int __init trace_init_flags_##name(void) \
+ { \
+ event_##name.perf_perm = &perf_perm_##name; \
+ return 0; \
+ } \
+ early_initcall(trace_init_flags_##name);
+
#define PERF_MAX_TRACE_SIZE 2048
#define MAX_FILTER_STR_VAL 256 /* Should handle KSYM_SYMBOL_LEN */
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index ebeab360d851..dd5cb1dca207 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -267,6 +267,8 @@ static inline void tracepoint_synchronize_unregister(void)
#define TRACE_EVENT_FLAGS(event, flag)
+#define TRACE_EVENT_PERF_PERM(event, expr)
+
#endif /* DECLARE_TRACE */
#ifndef TRACE_EVENT
@@ -399,4 +401,6 @@ static inline void tracepoint_synchronize_unregister(void)
#define TRACE_EVENT_FLAGS(event, flag)
+#define TRACE_EVENT_PERF_PERM(event, expr)
+
#endif /* ifdef TRACE_EVENT (see note above) */
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 5c7ab17cbb02..7bdda40fc406 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -90,6 +90,10 @@
#define TRACE_EVENT_FLAGS(name, value) \
__TRACE_EVENT_FLAGS(name, value)
+#undef TRACE_EVENT_PERF_PERM
+#define TRACE_EVENT_PERF_PERM(name, expr) \
+ __TRACE_EVENT_PERF_PERM(name, expr)
+
#include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
@@ -140,6 +144,9 @@
#undef TRACE_EVENT_FLAGS
#define TRACE_EVENT_FLAGS(event, flag)
+#undef TRACE_EVENT_PERF_PERM
+#define TRACE_EVENT_PERF_PERM(event, expr)
+
#include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
/*
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index 78e27e3b52ac..630889f68b1d 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -24,6 +24,12 @@ static int total_ref_count;
static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
struct perf_event *p_event)
{
+ if (tp_event->perf_perm) {
+ int ret = tp_event->perf_perm(tp_event, p_event);
+ if (ret)
+ return ret;
+ }
+
/* The ftrace function trace is allowed only for root. */
if (ftrace_event_is_function(tp_event) &&
perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
--
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