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Subject[PATCH] perf/core: make account/unaccount_sb_event consistent
Date
unaccount_pmu_sb_event did not check for attributes in event->attr
before calling detach_sb_event, while account_pmu_event did.

This caused NULL pointer reference in cgroup events that did not
have any of the attributes checked by account_pmu_event.

To trigger the bug just wait for a cgroup event to terminate, e.g.:

$ mkdir /dev/cgroup/devices/test
$ perf stat -e cycles -a -G test sleep 0

... see crash ...

Patch rebased on peterz/queue/perf/core .

Reviewed-by: Stephane Eranian <eranian@google.com>
Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
kernel/events/core.c | 34 ++++++++++++++++++----------------
1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1e48efc..6af0f01 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3682,15 +3682,28 @@ static void detach_sb_event(struct perf_event *event)
raw_spin_unlock(&pel->lock);
}

-static void unaccount_pmu_sb_event(struct perf_event *event)
+static bool is_sb_event(struct perf_event *event)
{
+ struct perf_event_attr *attr = &event->attr;
+
if (event->parent)
- return;
+ return false;

if (event->attach_state & PERF_ATTACH_TASK)
- return;
+ return false;

- detach_sb_event(event);
+ if (attr->mmap || attr->mmap_data || attr->mmap2 ||
+ attr->comm || attr->comm_exec ||
+ attr->task ||
+ attr->context_switch)
+ return true;
+ return false;
+}
+
+static void unaccount_pmu_sb_event(struct perf_event *event)
+{
+ if (is_sb_event(event))
+ detach_sb_event(event);
}

static void unaccount_event_cpu(struct perf_event *event, int cpu)
@@ -8666,18 +8679,7 @@ static void attach_sb_event(struct perf_event *event)
*/
static void account_pmu_sb_event(struct perf_event *event)
{
- struct perf_event_attr *attr = &event->attr;
-
- if (event->parent)
- return;
-
- if (event->attach_state & PERF_ATTACH_TASK)
- return;
-
- if (attr->mmap || attr->mmap_data || attr->mmap2 ||
- attr->comm || attr->comm_exec ||
- attr->task ||
- attr->context_switch)
+ if (is_sb_event(event))
attach_sb_event(event);
}

--
2.8.0.rc3.226.g39d4020
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