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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iwYHp-0006YG-Au; Tue, 28 Jan 2020 21:20:41 +0000 Received: from namei.org ([65.99.196.166]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iwYHY-0006B4-SF for linux-arm-kernel@lists.infradead.org; Tue, 28 Jan 2020 21:20:26 +0000 Received: from localhost (localhost [127.0.0.1]) by namei.org (8.14.4/8.14.4) with ESMTP id 00SLI4pL004594; Tue, 28 Jan 2020 21:18:04 GMT Date: Wed, 29 Jan 2020 08:18:04 +1100 (AEDT) From: James Morris To: Alexey Budankov Subject: Re: [PATCH v6 09/10] drivers/perf: open access for CAP_PERFMON privileged process In-Reply-To: Message-ID: References: <74d524ab-ac11-a7b8-1052-eba10f117e09@linux.intel.com> User-Agent: Alpine 2.21 (LRH 202 2017-01-01) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200128_132025_233259_38BD5E31 X-CRM114-Status: GOOD ( 13.29 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Song Liu , Peter Zijlstra , "benh@kernel.crashing.org" , Alexei Starovoitov , Lionel Landwerlin , "james.bottomley@hansenpartnership.com" , Paul Mackerras , Jiri Olsa , Andi Kleen , Michael Ellerman , Igor Lubashev , Alexander Shishkin , Ingo Molnar , oprofile-list@lists.sf.net, Serge Hallyn , Robert Richter , Will Deacon , "selinux@vger.kernel.org" , "intel-gfx@lists.freedesktop.org" , Arnaldo Carvalho de Melo , Stephane Eranian , Namhyung Kim , linux-arm-kernel , "linux-parisc@vger.kernel.org" , linux-kernel , "linux-perf-users@vger.kernel.org" , "linux-security-module@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 28 Jan 2020, Alexey Budankov wrote: > > Open access to monitoring for CAP_PERFMON privileged process. > Providing the access under CAP_PERFMON capability singly, without the > rest of CAP_SYS_ADMIN credentials, excludes chances to misuse the > credentials and makes operation more secure. > > CAP_PERFMON implements the principal of least privilege for performance > monitoring and observability operations (POSIX IEEE 1003.1e 2.2.2.39 principle > of least privilege: A security design principle that states that a process > or program be granted only those privileges (e.g., capabilities) necessary > to accomplish its legitimate function, and only for the time that such > privileges are actually required) > > For backward compatibility reasons access to the monitoring remains open > for CAP_SYS_ADMIN privileged processes but CAP_SYS_ADMIN usage for secure > monitoring is discouraged with respect to CAP_PERFMON capability. > > Signed-off-by: Alexey Budankov > --- > drivers/perf/arm_spe_pmu.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > Acked-by: James Morris > diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c > index 4e4984a55cd1..5dff81bc3324 100644 > --- a/drivers/perf/arm_spe_pmu.c > +++ b/drivers/perf/arm_spe_pmu.c > @@ -274,7 +274,7 @@ static u64 arm_spe_event_to_pmscr(struct perf_event *event) > if (!attr->exclude_kernel) > reg |= BIT(SYS_PMSCR_EL1_E1SPE_SHIFT); > > - if (IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR) && capable(CAP_SYS_ADMIN)) > + if (IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR) && perfmon_capable()) > reg |= BIT(SYS_PMSCR_EL1_CX_SHIFT); > > return reg; > @@ -700,7 +700,7 @@ static int arm_spe_pmu_event_init(struct perf_event *event) > return -EOPNOTSUPP; > > reg = arm_spe_event_to_pmscr(event); > - if (!capable(CAP_SYS_ADMIN) && > + if (!perfmon_capable() && > (reg & (BIT(SYS_PMSCR_EL1_PA_SHIFT) | > BIT(SYS_PMSCR_EL1_CX_SHIFT) | > BIT(SYS_PMSCR_EL1_PCT_SHIFT)))) > -- James Morris _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel