Em Mon, Aug 12, 2019 at 05:01:34PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Wed, Aug 07, 2019 at 10:44:15AM -0400, Igor Lubashev escreveu:
> > +++ b/tools/perf/util/evsel.c
> > @@ -279,7 +279,7 @@ struct evsel *perf_evsel__new_idx(struct
> > perf_event_attr *attr, int idx)
>
> > static bool perf_event_can_profile_kernel(void)
> > {
> > - return geteuid() == 0 || perf_event_paranoid() == -1;
> > + return perf_event_paranoid_check(-1);
> > }
>
> While looking at your changes I think the pre-existing code is wrong,
> i.e. the check in sys_perf_event_open(), in the kernel is:
>
> if (!attr.exclude_kernel) {
> if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
> return -EACCES;
> }
>
> And:
>
> static inline bool perf_paranoid_kernel(void)
> {
> return sysctl_perf_event_paranoid > 1;
> }
>
> So we have to change that perf_event_paranoit_check(-1) to pass 1
> instead?
>
> bool perf_event_paranoid_check(int max_level)
> {
> return perf_cap__capable(CAP_SYS_ADMIN) ||
> perf_event_paranoid() <= max_level;
> }
>
> Also you defined perf_cap__capable(anything) as:
>
> #ifdef HAVE_LIBCAP_SUPPORT
>
> #include <sys/capability.h>
>
> bool perf_cap__capable(cap_value_t cap);
>
> #else
>
> static inline bool perf_cap__capable(int cap __maybe_unused)
> {
> return false;
> }
>
> #endif /* HAVE_LIBCAP_SUPPORT */
>
>
> I think we should have:
>
> #else
>
> static inline bool perf_cap__capable(int cap __maybe_unused)
> {
> return geteuid() == 0;
> }
>
> #endif /* HAVE_LIBCAP_SUPPORT */
>
> Right?
>
> So I am removing the introduction of perf_cap__capable() from the first
> patch you sent, leaving it with _only_ the feature detection part, using
> that feature detection to do anything is then moved to a separate patch,
> after we finish this discussion about what we should fallback to when
> libcap-devel isn't available, i.e. we should use the previous checks,
> etc.
So, please take a look at the tmp.perf/cap branch in my git repo:
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/log/?h=tmp.perf/cap
I split the patch and made perf_cap__capable() fallback to 'return
geteuid() == 0;' when libcap-devel isn't available, i.e. keep the
checks made prior to your patchset.
Jiri, can I keep your Acked-by?
- Arnaldo
