[GIT PULL] perf fixes

From: Ingo Molnar
Date: Tue Sep 13 2016 - 14:14:40 EST

Linus,

Please pull the latest perf-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git perf-urgent-for-linus

# HEAD: 8ef9b8455a2a3049efa9e46e8a6402b972a3eb41 perf/x86/intel: Fix PEBSv3 record drain

This contains:

- A set of fixes found by directed-random perf fuzzing efforts by Vince Weaver,
Alexander Shishkin and Peter Zijlstra,

- a cqm driver crash fix,

- an AMD uncore driver use after free fix.

Thanks,

Ingo

------------------>
Alexander Shishkin (5):
perf/core: Fix a race between mmap_close() and set_output() of AUX events
perf/core: Fix aux_mmap_count vs aux_refcount order
perf/x86/intel/bts: Fix confused ordering of PMU callbacks
perf/x86/intel/bts: Fix BTS PMI detection
perf/x86/intel/bts: Kill a silly warning

Jiri Olsa (1):
perf/x86/intel/cqm: Check cqm/mbm enabled state in event init

Peter Zijlstra (2):
perf/core: Remove WARN from perf_event_read()
perf/x86/intel: Fix PEBSv3 record drain

Sebastian Andrzej Siewior (1):
perf/x86/amd/uncore: Prevent use after free


arch/x86/events/amd/uncore.c | 22 ++++++--
arch/x86/events/intel/bts.c | 123 +++++++++++++++++++++++++++++++++----------
arch/x86/events/intel/cqm.c | 9 ++++
arch/x86/events/intel/ds.c | 19 ++++---
kernel/events/core.c | 47 +++++++++++++----
kernel/events/ring_buffer.c | 15 ++++--
6 files changed, 180 insertions(+), 55 deletions(-)

diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
index e6131d4454e6..65577f081d07 100644
--- a/arch/x86/events/amd/uncore.c
+++ b/arch/x86/events/amd/uncore.c
@@ -29,6 +29,8 @@

#define COUNTER_SHIFT 16

+static HLIST_HEAD(uncore_unused_list);
+
struct amd_uncore {
int id;
int refcnt;
@@ -39,7 +41,7 @@ struct amd_uncore {
cpumask_t *active_mask;
struct pmu *pmu;
struct perf_event *events[MAX_COUNTERS];
- struct amd_uncore *free_when_cpu_online;
+ struct hlist_node node;
};

static struct amd_uncore * __percpu *amd_uncore_nb;
@@ -306,6 +308,7 @@ static int amd_uncore_cpu_up_prepare(unsigned int cpu)
uncore_nb->msr_base = MSR_F15H_NB_PERF_CTL;
uncore_nb->active_mask = &amd_nb_active_mask;
uncore_nb->pmu = &amd_nb_pmu;
+ uncore_nb->id = -1;
*per_cpu_ptr(amd_uncore_nb, cpu) = uncore_nb;
}

@@ -319,6 +322,7 @@ static int amd_uncore_cpu_up_prepare(unsigned int cpu)
uncore_l2->msr_base = MSR_F16H_L2I_PERF_CTL;
uncore_l2->active_mask = &amd_l2_active_mask;
uncore_l2->pmu = &amd_l2_pmu;
+ uncore_l2->id = -1;
*per_cpu_ptr(amd_uncore_l2, cpu) = uncore_l2;
}

@@ -348,7 +352,7 @@ amd_uncore_find_online_sibling(struct amd_uncore *this,
continue;

if (this->id == that->id) {
- that->free_when_cpu_online = this;
+ hlist_add_head(&this->node, &uncore_unused_list);
this = that;
break;
}
@@ -388,13 +392,23 @@ static int amd_uncore_cpu_starting(unsigned int cpu)
return 0;
}

+static void uncore_clean_online(void)
+{
+ struct amd_uncore *uncore;
+ struct hlist_node *n;
+
+ hlist_for_each_entry_safe(uncore, n, &uncore_unused_list, node) {
+ hlist_del(&uncore->node);
+ kfree(uncore);
+ }
+}
+
static void uncore_online(unsigned int cpu,
struct amd_uncore * __percpu *uncores)
{
struct amd_uncore *uncore = *per_cpu_ptr(uncores, cpu);

- kfree(uncore->free_when_cpu_online);
- uncore->free_when_cpu_online = NULL;
+ uncore_clean_online();

if (cpu == uncore->cpu)
cpumask_set_cpu(cpu, uncore->active_mask);
diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
index 0a6e393a2e62..bdcd6510992c 100644
--- a/arch/x86/events/intel/bts.c
+++ b/arch/x86/events/intel/bts.c
@@ -31,7 +31,17 @@
struct bts_ctx {
struct perf_output_handle handle;
struct debug_store ds_back;
- int started;
+ int state;
+};
+
+/* BTS context states: */
+enum {
+ /* no ongoing AUX transactions */
+ BTS_STATE_STOPPED = 0,
+ /* AUX transaction is on, BTS tracing is disabled */
+ BTS_STATE_INACTIVE,
+ /* AUX transaction is on, BTS tracing is running */
+ BTS_STATE_ACTIVE,
};

static DEFINE_PER_CPU(struct bts_ctx, bts_ctx);
@@ -204,6 +214,15 @@ static void bts_update(struct bts_ctx *bts)
static int
bts_buffer_reset(struct bts_buffer *buf, struct perf_output_handle *handle);

+/*
+ * Ordering PMU callbacks wrt themselves and the PMI is done by means
+ * of bts::state, which:
+ * - is set when bts::handle::event is valid, that is, between
+ * perf_aux_output_begin() and perf_aux_output_end();
+ * - is zero otherwise;
+ * - is ordered against bts::handle::event with a compiler barrier.
+ */
+
static void __bts_event_start(struct perf_event *event)
{
struct bts_ctx *bts = this_cpu_ptr(&bts_ctx);
@@ -221,10 +240,13 @@ static void __bts_event_start(struct perf_event *event)

/*
* local barrier to make sure that ds configuration made it
- * before we enable BTS
+ * before we enable BTS and bts::state goes ACTIVE
*/
wmb();

+ /* INACTIVE/STOPPED -> ACTIVE */
+ WRITE_ONCE(bts->state, BTS_STATE_ACTIVE);
+
intel_pmu_enable_bts(config);

}
@@ -251,9 +273,6 @@ static void bts_event_start(struct perf_event *event, int flags)

__bts_event_start(event);

- /* PMI handler: this counter is running and likely generating PMIs */
- ACCESS_ONCE(bts->started) = 1;
-
return;

fail_end_stop:
@@ -263,30 +282,34 @@ static void bts_event_start(struct perf_event *event, int flags)
event->hw.state = PERF_HES_STOPPED;
}

-static void __bts_event_stop(struct perf_event *event)
+static void __bts_event_stop(struct perf_event *event, int state)
{
+ struct bts_ctx *bts = this_cpu_ptr(&bts_ctx);
+
+ /* ACTIVE -> INACTIVE(PMI)/STOPPED(->stop()) */
+ WRITE_ONCE(bts->state, state);
+
/*
* No extra synchronization is mandated by the documentation to have
* BTS data stores globally visible.
*/
intel_pmu_disable_bts();
-
- if (event->hw.state & PERF_HES_STOPPED)
- return;
-
- ACCESS_ONCE(event->hw.state) |= PERF_HES_STOPPED;
}

static void bts_event_stop(struct perf_event *event, int flags)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
struct bts_ctx *bts = this_cpu_ptr(&bts_ctx);
- struct bts_buffer *buf = perf_get_aux(&bts->handle);
+ struct bts_buffer *buf = NULL;
+ int state = READ_ONCE(bts->state);

- /* PMI handler: don't restart this counter */
- ACCESS_ONCE(bts->started) = 0;
+ if (state == BTS_STATE_ACTIVE)
+ __bts_event_stop(event, BTS_STATE_STOPPED);

- __bts_event_stop(event);
+ if (state != BTS_STATE_STOPPED)
+ buf = perf_get_aux(&bts->handle);
+
+ event->hw.state |= PERF_HES_STOPPED;

if (flags & PERF_EF_UPDATE) {
bts_update(bts);
@@ -296,6 +319,7 @@ static void bts_event_stop(struct perf_event *event, int flags)
bts->handle.head =
local_xchg(&buf->data_size,
buf->nr_pages << PAGE_SHIFT);
+
perf_aux_output_end(&bts->handle, local_xchg(&buf->data_size, 0),
!!local_xchg(&buf->lost, 0));
}
@@ -310,8 +334,20 @@ static void bts_event_stop(struct perf_event *event, int flags)
void intel_bts_enable_local(void)
{
struct bts_ctx *bts = this_cpu_ptr(&bts_ctx);
+ int state = READ_ONCE(bts->state);
+
+ /*
+ * Here we transition from INACTIVE to ACTIVE;
+ * if we instead are STOPPED from the interrupt handler,
+ * stay that way. Can't be ACTIVE here though.
+ */
+ if (WARN_ON_ONCE(state == BTS_STATE_ACTIVE))
+ return;
+
+ if (state == BTS_STATE_STOPPED)
+ return;

- if (bts->handle.event && bts->started)
+ if (bts->handle.event)
__bts_event_start(bts->handle.event);
}

@@ -319,8 +355,15 @@ void intel_bts_disable_local(void)
{
struct bts_ctx *bts = this_cpu_ptr(&bts_ctx);

+ /*
+ * Here we transition from ACTIVE to INACTIVE;
+ * do nothing for STOPPED or INACTIVE.
+ */
+ if (READ_ONCE(bts->state) != BTS_STATE_ACTIVE)
+ return;
+
if (bts->handle.event)
- __bts_event_stop(bts->handle.event);
+ __bts_event_stop(bts->handle.event, BTS_STATE_INACTIVE);
}

static int
@@ -335,8 +378,6 @@ bts_buffer_reset(struct bts_buffer *buf, struct perf_output_handle *handle)
return 0;

head = handle->head & ((buf->nr_pages << PAGE_SHIFT) - 1);
- if (WARN_ON_ONCE(head != local_read(&buf->head)))
- return -EINVAL;

phys = &buf->buf[buf->cur_buf];
space = phys->offset + phys->displacement + phys->size - head;
@@ -403,22 +444,37 @@ bts_buffer_reset(struct bts_buffer *buf, struct perf_output_handle *handle)

int intel_bts_interrupt(void)
{
+ struct debug_store *ds = this_cpu_ptr(&cpu_hw_events)->ds;
struct bts_ctx *bts = this_cpu_ptr(&bts_ctx);
struct perf_event *event = bts->handle.event;
struct bts_buffer *buf;
s64 old_head;
- int err;
+ int err = -ENOSPC, handled = 0;

- if (!event || !bts->started)
- return 0;
+ /*
+ * The only surefire way of knowing if this NMI is ours is by checking
+ * the write ptr against the PMI threshold.
+ */
+ if (ds->bts_index >= ds->bts_interrupt_threshold)
+ handled = 1;
+
+ /*
+ * this is wrapped in intel_bts_enable_local/intel_bts_disable_local,
+ * so we can only be INACTIVE or STOPPED
+ */
+ if (READ_ONCE(bts->state) == BTS_STATE_STOPPED)
+ return handled;

buf = perf_get_aux(&bts->handle);
+ if (!buf)
+ return handled;
+
/*
* Skip snapshot counters: they don't use the interrupt, but
* there's no other way of telling, because the pointer will
* keep moving
*/
- if (!buf || buf->snapshot)
+ if (buf->snapshot)
return 0;

old_head = local_read(&buf->head);
@@ -426,18 +482,27 @@ int intel_bts_interrupt(void)

/* no new data */
if (old_head == local_read(&buf->head))
- return 0;
+ return handled;

perf_aux_output_end(&bts->handle, local_xchg(&buf->data_size, 0),
!!local_xchg(&buf->lost, 0));

buf = perf_aux_output_begin(&bts->handle, event);
- if (!buf)
- return 1;
+ if (buf)
+ err = bts_buffer_reset(buf, &bts->handle);
+
+ if (err) {
+ WRITE_ONCE(bts->state, BTS_STATE_STOPPED);

- err = bts_buffer_reset(buf, &bts->handle);
- if (err)
- perf_aux_output_end(&bts->handle, 0, false);
+ if (buf) {
+ /*
+ * BTS_STATE_STOPPED should be visible before
+ * cleared handle::event
+ */
+ barrier();
+ perf_aux_output_end(&bts->handle, 0, false);
+ }
+ }

return 1;
}
diff --git a/arch/x86/events/intel/cqm.c b/arch/x86/events/intel/cqm.c
index 783c49ddef29..8f82b02934fa 100644
--- a/arch/x86/events/intel/cqm.c
+++ b/arch/x86/events/intel/cqm.c
@@ -458,6 +458,11 @@ static void __intel_cqm_event_count(void *info);
static void init_mbm_sample(u32 rmid, u32 evt_type);
static void __intel_mbm_event_count(void *info);

+static bool is_cqm_event(int e)
+{
+ return (e == QOS_L3_OCCUP_EVENT_ID);
+}
+
static bool is_mbm_event(int e)
{
return (e >= QOS_MBM_TOTAL_EVENT_ID && e <= QOS_MBM_LOCAL_EVENT_ID);
@@ -1366,6 +1371,10 @@ static int intel_cqm_event_init(struct perf_event *event)
(event->attr.config > QOS_MBM_LOCAL_EVENT_ID))
return -EINVAL;

+ if ((is_cqm_event(event->attr.config) && !cqm_enabled) ||
+ (is_mbm_event(event->attr.config) && !mbm_enabled))
+ return -EINVAL;
+
/* unsupported modes and filters */
if (event->attr.exclude_user ||
event->attr.exclude_kernel ||
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 7ce9f3f669e6..9b983a474253 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1274,18 +1274,18 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
struct pebs_record_nhm *p = at;
u64 pebs_status;

- /* PEBS v3 has accurate status bits */
+ pebs_status = p->status & cpuc->pebs_enabled;
+ pebs_status &= (1ULL << x86_pmu.max_pebs_events) - 1;
+
+ /* PEBS v3 has more accurate status bits */
if (x86_pmu.intel_cap.pebs_format >= 3) {
- for_each_set_bit(bit, (unsigned long *)&p->status,
- MAX_PEBS_EVENTS)
+ for_each_set_bit(bit, (unsigned long *)&pebs_status,
+ x86_pmu.max_pebs_events)
counts[bit]++;

continue;
}

- pebs_status = p->status & cpuc->pebs_enabled;
- pebs_status &= (1ULL << x86_pmu.max_pebs_events) - 1;
-
/*
* On some CPUs the PEBS status can be zero when PEBS is
* racing with clearing of GLOBAL_STATUS.
@@ -1333,8 +1333,11 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
continue;

event = cpuc->events[bit];
- WARN_ON_ONCE(!event);
- WARN_ON_ONCE(!event->attr.precise_ip);
+ if (WARN_ON_ONCE(!event))
+ continue;
+
+ if (WARN_ON_ONCE(!event->attr.precise_ip))
+ continue;

/* log dropped samples number */
if (error[bit])
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3cfabdf7b942..a54f2c2cdb20 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2496,11 +2496,11 @@ static int __perf_event_stop(void *info)
return 0;
}

-static int perf_event_restart(struct perf_event *event)
+static int perf_event_stop(struct perf_event *event, int restart)
{
struct stop_event_data sd = {
.event = event,
- .restart = 1,
+ .restart = restart,
};
int ret = 0;

@@ -3549,10 +3549,18 @@ static int perf_event_read(struct perf_event *event, bool group)
.group = group,
.ret = 0,
};
- ret = smp_call_function_single(event->oncpu, __perf_event_read, &data, 1);
- /* The event must have been read from an online CPU: */
- WARN_ON_ONCE(ret);
- ret = ret ? : data.ret;
+ /*
+ * Purposely ignore the smp_call_function_single() return
+ * value.
+ *
+ * If event->oncpu 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(event->oncpu, __perf_event_read, &data, 1);
+ ret = data.ret;
} else if (event->state == PERF_EVENT_STATE_INACTIVE) {
struct perf_event_context *ctx = event->ctx;
unsigned long flags;
@@ -4837,6 +4845,19 @@ static void ring_buffer_attach(struct perf_event *event,
spin_unlock_irqrestore(&rb->event_lock, flags);
}

+ /*
+ * Avoid racing with perf_mmap_close(AUX): stop the event
+ * before swizzling the event::rb pointer; if it's getting
+ * unmapped, its aux_mmap_count will be 0 and it won't
+ * restart. See the comment in __perf_pmu_output_stop().
+ *
+ * Data will inevitably be lost when set_output is done in
+ * mid-air, but then again, whoever does it like this is
+ * not in for the data anyway.
+ */
+ if (has_aux(event))
+ perf_event_stop(event, 0);
+
rcu_assign_pointer(event->rb, rb);

if (old_rb) {
@@ -6112,7 +6133,7 @@ static void perf_event_addr_filters_exec(struct perf_event *event, void *data)
raw_spin_unlock_irqrestore(&ifh->lock, flags);

if (restart)
- perf_event_restart(event);
+ perf_event_stop(event, 1);
}

void perf_event_exec(void)
@@ -6156,7 +6177,13 @@ static void __perf_event_output_stop(struct perf_event *event, void *data)

/*
* In case of inheritance, it will be the parent that links to the
- * ring-buffer, but it will be the child that's actually using it:
+ * ring-buffer, but it will be the child that's actually using it.
+ *
+ * We are using event::rb to determine if the event should be stopped,
+ * however this may race with ring_buffer_attach() (through set_output),
+ * which will make us skip the event that actually needs to be stopped.
+ * So ring_buffer_attach() has to stop an aux event before re-assigning
+ * its rb pointer.
*/
if (rcu_dereference(parent->rb) == rb)
ro->err = __perf_event_stop(&sd);
@@ -6670,7 +6697,7 @@ static void __perf_addr_filters_adjust(struct perf_event *event, void *data)
raw_spin_unlock_irqrestore(&ifh->lock, flags);

if (restart)
- perf_event_restart(event);
+ perf_event_stop(event, 1);
}

/*
@@ -7859,7 +7886,7 @@ static void perf_event_addr_filters_apply(struct perf_event *event)
mmput(mm);

restart:
- perf_event_restart(event);
+ perf_event_stop(event, 1);
}

/*
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index ae9b90dc9a5a..257fa460b846 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -330,15 +330,22 @@ void *perf_aux_output_begin(struct perf_output_handle *handle,
if (!rb)
return NULL;

- if (!rb_has_aux(rb) || !atomic_inc_not_zero(&rb->aux_refcount))
+ if (!rb_has_aux(rb))
goto err;

/*
- * If rb::aux_mmap_count is zero (and rb_has_aux() above went through),
- * the aux buffer is in perf_mmap_close(), about to get freed.
+ * If aux_mmap_count is zero, the aux buffer is in perf_mmap_close(),
+ * about to get freed, so we leave immediately.
+ *
+ * Checking rb::aux_mmap_count and rb::refcount has to be done in
+ * the same order, see perf_mmap_close. Otherwise we end up freeing
+ * aux pages in this path, which is a bug, because in_atomic().
*/
if (!atomic_read(&rb->aux_mmap_count))
- goto err_put;
+ goto err;
+
+ if (!atomic_inc_not_zero(&rb->aux_refcount))
+ goto err;

/*
* Nesting is not supported for AUX area, make sure nested