perf: Apply PERF_EVENT_IOC_MODIFY_ATTRIBUTES to children

As with other ioctls (such as PERF_EVENT_IOC_{ENABLE,DISABLE}), fix up
handling of PERF_EVENT_IOC_MODIFY_ATTRIBUTES to also apply to children.

Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Link: https://lkml.kernel.org/r/20210408103605.1676875-3-elver@google.com

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 318ff7b..10ed2cd 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3200,16 +3200,36 @@ static int perf_event_modify_breakpoint(struct perf_event *bp,
 static int perf_event_modify_attr(struct perf_event *event,
                                  struct perf_event_attr *attr)
 {
+       int (*func)(struct perf_event *, struct perf_event_attr *);
+       struct perf_event *child;
+       int err;
+
        if (event->attr.type != attr->type)
                return -EINVAL;
 
        switch (event->attr.type) {
        case PERF_TYPE_BREAKPOINT:
-               return perf_event_modify_breakpoint(event, attr);
+               func = perf_event_modify_breakpoint;
+               break;
        default:
                /* Place holder for future additions. */
                return -EOPNOTSUPP;
        }
+
+       WARN_ON_ONCE(event->ctx->parent_ctx);
+
+       mutex_lock(&event->child_mutex);
+       err = func(event, attr);
+       if (err)
+               goto out;
+       list_for_each_entry(child, &event->child_list, child_list) {
+               err = func(child, attr);
+               if (err)
+                       goto out;
+       }
+out:
+       mutex_unlock(&event->child_mutex);
+       return err;
 }
 
 static void ctx_sched_out(struct perf_event_context *ctx,