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[187.26.98.68]) by smtp.gmail.com with ESMTPSA id f22sm5634753qkh.55.2019.08.12.13.01.37 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 12 Aug 2019 13:01:38 -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 D585740340; Mon, 12 Aug 2019 17:01:34 -0300 (-03) Date: Mon, 12 Aug 2019 17:01:34 -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: <20190812200134.GE9280@kernel.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 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. - Arnaldo