Re: [PATCH v8 1/6] perf: Add PERF_RECORD_NAMESPACES to include namespaces related info

From: Arnaldo Carvalho de Melo
Date: Mon Mar 13 2017 - 15:53:15 EST

Em Wed, Mar 08, 2017 at 02:11:36AM +0530, Hari Bathini escreveu:
> @@ -9691,6 +9825,11 @@ SYSCALL_DEFINE5(perf_event_open,
> return -EACCES;
> }
> + if (attr.namespaces) {
> + if (!capable(CAP_SYS_ADMIN))
> + return -EACCES;
> + }
> +

So, testing the first tooling patch I get:

[acme@jouet linux]$ perf record --namespaces ls
You may not have permission to collect stats.

Consider tweaking /proc/sys/kernel/perf_event_paranoid,
which controls use of the performance events system by
unprivileged users (without CAP_SYS_ADMIN).

The current value is 2:

-1: Allow use of (almost) all events by all users
>= 0: Disallow raw tracepoint access by users without CAP_IOC_LOCK
>= 1: Disallow CPU event access by users without CAP_SYS_ADMIN
>= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN

To make this setting permanent, edit /etc/sysctl.conf too, e.g.:

kernel.perf_event_paranoid = -1

[acme@jouet linux]$

----------------------- 8< ---------------------------------------

So this specific case is not related to perf_event_paranoid, we need to
improve error handling here, i.e. see attr.namespaces, !CAP_SYS_ADMIN,
-EACCESS at sys_perf_event_open() -> better error message.

And perhaps we make an extra check about perf_event_paranoid... Ingo? Peter?

Can be done as a follow up patch tho, just adding entry to the collective TODO

- Arnaldo