This is a note to let you know that I've just added the patch titled
perf: Fix PERF_EVENT_IOC_PERIOD migration race
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-fix-perf_event_ioc_period-migration-race.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c7999c6f3fed9e383d3131474588f282ae6d56b9 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Tue, 4 Aug 2015 19:22:49 +0200
Subject: perf: Fix PERF_EVENT_IOC_PERIOD migration race
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
commit c7999c6f3fed9e383d3131474588f282ae6d56b9 upstream.
I ran the perf fuzzer, which triggered some WARN()s which are due to
trying to stop/restart an event on the wrong CPU.
Use the normal IPI pattern to ensure we run the code on the correct CPU.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Fixes: bad7192b842c ("perf: Fix PERF_EVENT_IOC_PERIOD to force-reset the period")
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/events/core.c | 75 +++++++++++++++++++++++++++++++++++++--------------
1 file changed, 55 insertions(+), 20 deletions(-)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3562,28 +3562,21 @@ static void perf_event_for_each(struct p
mutex_unlock(&ctx->mutex);
}
-static int perf_event_period(struct perf_event *event, u64 __user *arg)
-{
- struct perf_event_context *ctx = event->ctx;
- int ret = 0, active;
+struct period_event {
+ struct perf_event *event;
u64 value;
+};
- if (!is_sampling_event(event))
- return -EINVAL;
-
- if (copy_from_user(&value, arg, sizeof(value)))
- return -EFAULT;
-
- if (!value)
- return -EINVAL;
+static int __perf_event_period(void *info)
+{
+ struct period_event *pe = info;
+ struct perf_event *event = pe->event;
+ struct perf_event_context *ctx = event->ctx;
+ u64 value = pe->value;
+ bool active;
- raw_spin_lock_irq(&ctx->lock);
+ raw_spin_lock(&ctx->lock);
if (event->attr.freq) {
- if (value > sysctl_perf_event_sample_rate) {
- ret = -EINVAL;
- goto unlock;
- }
-
event->attr.sample_freq = value;
} else {
event->attr.sample_period = value;
@@ -3602,11 +3595,53 @@ static int perf_event_period(struct perf
event->pmu->start(event, PERF_EF_RELOAD);
perf_pmu_enable(ctx->pmu);
}
+ raw_spin_unlock(&ctx->lock);
+
+ return 0;
+}
+
+static int perf_event_period(struct perf_event *event, u64 __user *arg)
+{
+ struct period_event pe = { .event = event, };
+ struct perf_event_context *ctx = event->ctx;
+ struct task_struct *task;
+ u64 value;
+
+ if (!is_sampling_event(event))
+ return -EINVAL;
+
+ if (copy_from_user(&value, arg, sizeof(value)))
+ return -EFAULT;
+
+ if (!value)
+ return -EINVAL;
+
+ if (event->attr.freq && value > sysctl_perf_event_sample_rate)
+ return -EINVAL;
+
+ task = ctx->task;
+ pe.value = value;
+
+ if (!task) {
+ cpu_function_call(event->cpu, __perf_event_period, &pe);
+ return 0;
+ }
+
+retry:
+ if (!task_function_call(task, __perf_event_period, &pe))
+ return 0;
+
+ raw_spin_lock_irq(&ctx->lock);
+ if (ctx->is_active) {
+ raw_spin_unlock_irq(&ctx->lock);
+ task = ctx->task;
+ goto retry;
+ }
-unlock:
+ __perf_event_period(&pe);
raw_spin_unlock_irq(&ctx->lock);
- return ret;
+ return 0;
}
static const struct file_operations perf_fops;
Patches currently in stable-queue which might be from peterz@xxxxxxxxxxxxx are
queue-3.14/perf-fix-perf_event_ioc_period-migration-race.patch
queue-3.14/ipc-sem.c-update-correct-memory-barriers.patch
queue-3.14/perf-fix-fasync-handling-on-inherited-events.patch
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