From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753640AbbH0PN6 (ORCPT ); Thu, 27 Aug 2015 11:13:58 -0400 Received: from mga11.intel.com ([192.55.52.93]:30191 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752375AbbH0PN5 (ORCPT ); Thu, 27 Aug 2015 11:13:57 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.17,422,1437462000"; d="scan'208";a="756563361" From: Alexander Shishkin To: Peter Zijlstra Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo , Alexander Shishkin Subject: [PATCH 2/2] perf/x86/intel/bts: Disallow use by unprivileged users on paranoid systems Date: Thu, 27 Aug 2015 18:13:42 +0300 Message-Id: <1440688422-27954-3-git-send-email-alexander.shishkin@linux.intel.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1440688422-27954-1-git-send-email-alexander.shishkin@linux.intel.com> References: <1440688422-27954-1-git-send-email-alexander.shishkin@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org BTS leaks kernel addresses even in userspace-only mode due to imprecise IP sampling, so sometimes syscall entry points or page fault handler addresses end up in a userspace trace. Now, intel_bts driver exports trace data zero-copy, it does not scan through it to filter out the kernel addresses and it's would be a O(n) job. To work around this situation, this patch forbids the use of intel_bts driver by unprivileged users with paranoid setting higher than 1, which forbids kernel tracing. Signed-off-by: Alexander Shishkin --- arch/x86/kernel/cpu/perf_event_intel_bts.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/kernel/cpu/perf_event_intel_bts.c b/arch/x86/kernel/cpu/perf_event_intel_bts.c index 80df16e020..4f6daff92d 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_bts.c +++ b/arch/x86/kernel/cpu/perf_event_intel_bts.c @@ -495,6 +495,16 @@ static int bts_event_init(struct perf_event *event) if (x86_add_exclusive(x86_lbr_exclusive_bts)) return -EBUSY; + /* + * BTS leaks kernel addresses even when CPL0 tracing is + * disabled, so disallow intel_bts driver for unprivileged + * users on paranoid systems since it provides trace data + * to the user in a zero-copy fashion. + */ + if (event->attr.exclude_kernel && perf_paranoid_kernel() && + !capable(CAP_SYS_ADMIN)) + return -EACCES; + ret = x86_reserve_hardware(); if (ret) { x86_del_exclusive(x86_lbr_exclusive_bts); -- 2.5.0