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 <[email protected]> Signed-off-by: David Carrillo-Cisneros <[email protected]> --- 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
