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SubjectRe: System crash with perf_fuzzer (kernel: 5.0.0-rc3)
On Thu, Jan 31, 2019 at 09:27:11AM +0100, Jiri Olsa wrote:
> On Wed, Jan 30, 2019 at 07:36:48PM +0100, Jiri Olsa wrote:
>
> SNIP
>
> > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > index 280a72b3a553..22ec63a0782e 100644
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -4969,6 +4969,26 @@ static void __perf_event_period(struct perf_event *event,
> > }
> > }
> >
> > +static int check_period(struct perf_event *event, u64 value)
> > +{
> > + u64 sample_period_attr = event->attr.sample_period;
> > + u64 sample_period_hw = event->hw.sample_period;
> > + int ret;
> > +
> > + if (event->attr.freq) {
> > + event->attr.sample_freq = value;
> > + } else {
> > + event->attr.sample_period = value;
> > + event->hw.sample_period = value;
> > + }
>
> hm, I think we need to check the period without changing the event,
> because we don't disable pmu, so it might get picked up by bts code
>
> will check

with attached patch I did not trigger the fuzzer crash
for over a day now, could you guys try?

thanks,
jirka


---
arch/x86/events/core.c | 14 ++++++++++++++
arch/x86/events/intel/core.c | 9 +++++++++
arch/x86/events/perf_event.h | 16 ++++++++++++++--
include/linux/perf_event.h | 5 +++++
kernel/events/core.c | 16 ++++++++++++++++
5 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 374a19712e20..b684f0294f35 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2278,6 +2278,19 @@ void perf_check_microcode(void)
x86_pmu.check_microcode();
}

+static int x86_pmu_check_period(struct perf_event *event, u64 value)
+{
+ if (x86_pmu.check_period && x86_pmu.check_period(event, value))
+ return -EINVAL;
+
+ if (value && x86_pmu.limit_period) {
+ if (x86_pmu.limit_period(event, value) > value)
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static struct pmu pmu = {
.pmu_enable = x86_pmu_enable,
.pmu_disable = x86_pmu_disable,
@@ -2302,6 +2315,7 @@ static struct pmu pmu = {
.event_idx = x86_pmu_event_idx,
.sched_task = x86_pmu_sched_task,
.task_ctx_size = sizeof(struct x86_perf_task_context),
+ .check_period = x86_pmu_check_period,
};

void arch_perf_update_userpage(struct perf_event *event,
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 8b4e3020aba2..a3fbbd33beef 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3586,6 +3586,11 @@ static void intel_pmu_sched_task(struct perf_event_context *ctx,
intel_pmu_lbr_sched_task(ctx, sched_in);
}

+static int intel_pmu_check_period(struct perf_event *event, u64 value)
+{
+ return intel_pmu_has_bts_period(event, value) ? -EINVAL : 0;
+}
+
PMU_FORMAT_ATTR(offcore_rsp, "config1:0-63");

PMU_FORMAT_ATTR(ldlat, "config1:0-15");
@@ -3665,6 +3670,8 @@ static __initconst const struct x86_pmu core_pmu = {
.cpu_prepare = intel_pmu_cpu_prepare,
.cpu_starting = intel_pmu_cpu_starting,
.cpu_dying = intel_pmu_cpu_dying,
+
+ .check_period = intel_pmu_check_period,
};

static struct attribute *intel_pmu_attrs[];
@@ -3707,6 +3714,8 @@ static __initconst const struct x86_pmu intel_pmu = {
.cpu_dying = intel_pmu_cpu_dying,
.guest_get_msrs = intel_guest_get_msrs,
.sched_task = intel_pmu_sched_task,
+
+ .check_period = intel_pmu_check_period,
};

static __init void intel_clovertown_quirk(void)
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 78d7b7031bfc..d46fd6754d92 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -646,6 +646,11 @@ struct x86_pmu {
* Intel host/guest support (KVM)
*/
struct perf_guest_switch_msr *(*guest_get_msrs)(int *nr);
+
+ /*
+ * Check period value for PERF_EVENT_IOC_PERIOD ioctl.
+ */
+ int (*check_period) (struct perf_event *event, u64 period);
};

struct x86_perf_task_context {
@@ -857,7 +862,7 @@ static inline int amd_pmu_init(void)

#ifdef CONFIG_CPU_SUP_INTEL

-static inline bool intel_pmu_has_bts(struct perf_event *event)
+static inline bool intel_pmu_has_bts_period(struct perf_event *event, u64 period)
{
struct hw_perf_event *hwc = &event->hw;
unsigned int hw_event, bts_event;
@@ -868,7 +873,14 @@ static inline bool intel_pmu_has_bts(struct perf_event *event)
hw_event = hwc->config & INTEL_ARCH_EVENT_MASK;
bts_event = x86_pmu.event_map(PERF_COUNT_HW_BRANCH_INSTRUCTIONS);

- return hw_event == bts_event && hwc->sample_period == 1;
+ return hw_event == bts_event && period == 1;
+}
+
+static inline bool intel_pmu_has_bts(struct perf_event *event)
+{
+ struct hw_perf_event *hwc = &event->hw;
+
+ return intel_pmu_has_bts_period(event, hwc->sample_period);
}

int intel_pmu_save_and_restart(struct perf_event *event);
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index f2f9f8592d42..0a7d4d6a3660 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -447,6 +447,11 @@ struct pmu {
* Filter events for PMU-specific reasons.
*/
int (*filter_match) (struct perf_event *event); /* optional */
+
+ /*
+ * Check period value for PERF_EVENT_IOC_PERIOD ioctl.
+ */
+ int (*check_period) (struct perf_event *event, u64 value); /* optional */
};

enum perf_addr_filter_action_t {
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 214c434ddc1b..edd92dc556fb 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4969,6 +4969,11 @@ static void __perf_event_period(struct perf_event *event,
}
}

+static int perf_event_check_period(struct perf_event *event, u64 value)
+{
+ return event->pmu->check_period(event, value);
+}
+
static int perf_event_period(struct perf_event *event, u64 __user *arg)
{
u64 value;
@@ -4985,6 +4990,9 @@ static int perf_event_period(struct perf_event *event, u64 __user *arg)
if (event->attr.freq && value > sysctl_perf_event_sample_rate)
return -EINVAL;

+ if (perf_event_check_period(event, value))
+ return -EINVAL;
+
event_function_call(event, __perf_event_period, &value);

return 0;
@@ -9601,6 +9609,11 @@ static int perf_pmu_nop_int(struct pmu *pmu)
return 0;
}

+static int perf_event_nop_int(struct perf_event *event, u64 value)
+{
+ return 0;
+}
+
static DEFINE_PER_CPU(unsigned int, nop_txn_flags);

static void perf_pmu_start_txn(struct pmu *pmu, unsigned int flags)
@@ -9901,6 +9914,9 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type)
pmu->pmu_disable = perf_pmu_nop_void;
}

+ if (!pmu->check_period)
+ pmu->check_period = perf_event_nop_int;
+
if (!pmu->event_idx)
pmu->event_idx = perf_event_idx_default;

--
2.17.2
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