Commit-ID: 451d24d1e5f40bad000fa9abe36ddb16fc9928cb
Gitweb: http://git.kernel.org/tip/451d24d1e5f40bad000fa9abe36ddb16fc9928cb
Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Tue, 31 Jan 2017 11:27:10 +0100
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Fri, 10 Feb 2017 09:04:50 +0100
perf/core: Fix crash in perf_event_read()
Alexei had his box explode because doing read() on a package
(rapl/uncore) event that isn't currently scheduled in ends up doing an
out-of-bounds load.
Rework the code to more explicitly deal with event->oncpu being -1.
Reported-by: Alexei Starovoitov <alexei.starovoi...@gmail.com>
Tested-by: Alexei Starovoitov <a...@kernel.org>
Tested-by: David Carrillo-Cisneros <davi...@google.com>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: eran...@google.com
Fixes: d6a2f9035bfc ("perf/core: Introduce PMU_EV_CAP_READ_ACTIVE_PKG")
Link:
http://lkml.kernel.org/r/20170131102710.gl6...@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
kernel/events/core.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index e5aaa80..e235bb9 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3487,14 +3487,15 @@ struct perf_read_data {
int ret;
};
-static int find_cpu_to_read(struct perf_event *event, int local_cpu)
+static int __perf_event_read_cpu(struct perf_event *event, int event_cpu)
{
- int event_cpu = event->oncpu;
u16 local_pkg, event_pkg;
if (event->group_caps & PERF_EV_CAP_READ_ACTIVE_PKG) {
- event_pkg = topology_physical_package_id(event_cpu);
- local_pkg = topology_physical_package_id(local_cpu);
+ int local_cpu = smp_processor_id();
+
+ event_pkg = topology_physical_package_id(event_cpu);
+ local_pkg = topology_physical_package_id(local_cpu);
if (event_pkg == local_pkg)
return local_cpu;
@@ -3624,7 +3625,7 @@ u64 perf_event_read_local(struct perf_event *event)
static int perf_event_read(struct perf_event *event, bool group)
{
- int ret = 0, cpu_to_read, local_cpu;
+ int event_cpu, ret = 0;
/*
* If event is enabled and currently active on a CPU, update the
@@ -3637,21 +3638,25 @@ static int perf_event_read(struct perf_event *event,
bool group)
.ret = 0,
};
- local_cpu = get_cpu();
- cpu_to_read = find_cpu_to_read(event, local_cpu);
- put_cpu();
+ event_cpu = READ_ONCE(event->oncpu);
+ if ((unsigned)event_cpu >= nr_cpu_ids)
+ return 0;
+
+ preempt_disable();
+ event_cpu = __perf_event_read_cpu(event, event_cpu);
/*
* Purposely ignore the smp_call_function_single() return
* value.
*
- * If event->oncpu isn't a valid CPU it means the event got
+ * If event_cpu isn't a valid CPU it means the event got
* scheduled out and that will have updated the event count.
*
* Therefore, either way, we'll have an up-to-date event count
* after this.
*/
- (void)smp_call_function_single(cpu_to_read, __perf_event_read,
&data, 1);
+ (void)smp_call_function_single(event_cpu, __perf_event_read,
&data, 1);
+ preempt_enable();
ret = data.ret;
} else if (event->state == PERF_EVENT_STATE_INACTIVE) {
struct perf_event_context *ctx = event->ctx;
