Messages in this thread | | | From | Arnaldo Carvalho de Melo <> | Date | Mon, 12 Aug 2019 17:15:57 -0300 | Subject | Re: [PATCH v3 2/4] perf: Use CAP_SYS_ADMIN with perf_event_paranoid checks |
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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
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