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[187.26.98.68]) by smtp.gmail.com with ESMTPSA id d123sm49214177qkb.94.2019.08.12.13.16.00 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 12 Aug 2019 13:16:01 -0700 (PDT) From: Arnaldo Carvalho de Melo X-Google-Original-From: Arnaldo Carvalho de Melo Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 7243E40340; Mon, 12 Aug 2019 17:15:57 -0300 (-03) Date: Mon, 12 Aug 2019 17:15:57 -0300 To: Igor Lubashev Cc: linux-kernel@vger.kernel.org, Jiri Olsa , Alexey Budankov , Peter Zijlstra , Ingo Molnar , Mathieu Poirier , Alexander Shishkin , Namhyung Kim , Suzuki K Poulose , linux-arm-kernel@lists.infradead.org, James Morris Subject: Re: [PATCH v3 2/4] perf: Use CAP_SYS_ADMIN with perf_event_paranoid checks Message-ID: <20190812201557.GF9280@kernel.org> References: <20190812200134.GE9280@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190812200134.GE9280@kernel.org> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.12.0 (2019-05-25) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > > 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