perf: Ensure consistent inherit state in groups

Make sure all events in a group have the same inherit state. It was
possible for group leaders to have inherit set while sibling events
would not have inherit set.

In this case we'd still inherit the siblings, leading to some
non-fatal weirdness.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-r32tt8yldvic3jlcghd3g35u@git.kernel.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

kernel/events/core.c

@@ -7081,20 +7081,26 @@ SYSCALL_DEFINE5(perf_event_open,
 		}
 	}
 
+	if (task && group_leader &&
+	    group_leader->attr.inherit != attr.inherit) {
+		err = -EINVAL;
+		goto err_task;
+	}
+
 	get_online_cpus();
 
 	event = perf_event_alloc(&attr, cpu, task, group_leader, NULL,
 				 NULL, NULL);
 	if (IS_ERR(event)) {
 		err = PTR_ERR(event);
-		goto err_task;
+		goto err_cpus;
 	}
 
 	if (flags & PERF_FLAG_PID_CGROUP) {
 		err = perf_cgroup_connect(pid, event, &attr, group_leader);
 		if (err) {
 			__free_event(event);
-			goto err_task;
+			goto err_cpus;
 		}
 	}
 
@@ -7256,8 +7262,9 @@ SYSCALL_DEFINE5(perf_event_open,
 	put_ctx(ctx);
 err_alloc:
 	free_event(event);
-err_task:
+err_cpus:
 	put_online_cpus();
+err_task:
 	if (task)
 		put_task_struct(task);
 err_group_fd: