Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756474AbdHYL5u (ORCPT ); Fri, 25 Aug 2017 07:57:50 -0400 Received: from terminus.zytor.com ([65.50.211.136]:47465 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756457AbdHYL5s (ORCPT ); Fri, 25 Aug 2017 07:57:48 -0400 Date: Fri, 25 Aug 2017 04:51:58 -0700 From: tip-bot for Mark Rutland Message-ID: Cc: zhouchengming1@huawei.com, mark.rutland@arm.com, torvalds@linux-foundation.org, mingo@kernel.org, tglx@linutronix.de, alexander.shishkin@linux.intel.com, acme@kernel.org, peterz@infradead.org, hpa@zytor.com, linux-kernel@vger.kernel.org Reply-To: peterz@infradead.org, acme@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com, alexander.shishkin@linux.intel.com, tglx@linutronix.de, mingo@kernel.org, torvalds@linux-foundation.org, mark.rutland@arm.com, zhouchengming1@huawei.com In-Reply-To: <1498142498-15758-1-git-send-email-mark.rutland@arm.com> References: <1498142498-15758-1-git-send-email-mark.rutland@arm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] perf/core: Fix group {cpu,task} validation Git-Commit-ID: 64aee2a965cf2954a038b5522f11d2cd2f0f8f3e X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5705 Lines: 183 Commit-ID: 64aee2a965cf2954a038b5522f11d2cd2f0f8f3e Gitweb: http://git.kernel.org/tip/64aee2a965cf2954a038b5522f11d2cd2f0f8f3e Author: Mark Rutland AuthorDate: Thu, 22 Jun 2017 15:41:38 +0100 Committer: Ingo Molnar CommitDate: Fri, 25 Aug 2017 11:00:34 +0200 perf/core: Fix group {cpu,task} validation Regardless of which events form a group, it does not make sense for the events to target different tasks and/or CPUs, as this leaves the group inconsistent and impossible to schedule. The core perf code assumes that these are consistent across (successfully intialised) groups. Core perf code only verifies this when moving SW events into a HW context. Thus, we can violate this requirement for pure SW groups and pure HW groups, unless the relevant PMU driver happens to perform this verification itself. These mismatched groups subsequently wreak havoc elsewhere. For example, we handle watchpoints as SW events, and reserve watchpoint HW on a per-CPU basis at pmu::event_init() time to ensure that any event that is initialised is guaranteed to have a slot at pmu::add() time. However, the core code only checks the group leader's cpu filter (via event_filter_match()), and can thus install follower events onto CPUs violating thier (mismatched) CPU filters, potentially installing them into a CPU without sufficient reserved slots. This can be triggered with the below test case, resulting in warnings from arch backends. #define _GNU_SOURCE #include #include #include #include #include #include #include static int perf_event_open(struct perf_event_attr *attr, pid_t pid, int cpu, int group_fd, unsigned long flags) { return syscall(__NR_perf_event_open, attr, pid, cpu, group_fd, flags); } char watched_char; struct perf_event_attr wp_attr = { .type = PERF_TYPE_BREAKPOINT, .bp_type = HW_BREAKPOINT_RW, .bp_addr = (unsigned long)&watched_char, .bp_len = 1, .size = sizeof(wp_attr), }; int main(int argc, char *argv[]) { int leader, ret; cpu_set_t cpus; /* * Force use of CPU0 to ensure our CPU0-bound events get scheduled. */ CPU_ZERO(&cpus); CPU_SET(0, &cpus); ret = sched_setaffinity(0, sizeof(cpus), &cpus); if (ret) { printf("Unable to set cpu affinity\n"); return 1; } /* open leader event, bound to this task, CPU0 only */ leader = perf_event_open(&wp_attr, 0, 0, -1, 0); if (leader < 0) { printf("Couldn't open leader: %d\n", leader); return 1; } /* * Open a follower event that is bound to the same task, but a * different CPU. This means that the group should never be possible to * schedule. */ ret = perf_event_open(&wp_attr, 0, 1, leader, 0); if (ret < 0) { printf("Couldn't open mismatched follower: %d\n", ret); return 1; } else { printf("Opened leader/follower with mismastched CPUs\n"); } /* * Open as many independent events as we can, all bound to the same * task, CPU0 only. */ do { ret = perf_event_open(&wp_attr, 0, 0, -1, 0); } while (ret >= 0); /* * Force enable/disble all events to trigger the erronoeous * installation of the follower event. */ printf("Opened all events. Toggling..\n"); for (;;) { prctl(PR_TASK_PERF_EVENTS_DISABLE, 0, 0, 0, 0); prctl(PR_TASK_PERF_EVENTS_ENABLE, 0, 0, 0, 0); } return 0; } Fix this by validating this requirement regardless of whether we're moving events. Signed-off-by: Mark Rutland Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Zhou Chengming Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1498142498-15758-1-git-send-email-mark.rutland@arm.com Signed-off-by: Ingo Molnar --- kernel/events/core.c | 39 +++++++++++++++++++-------------------- 1 file changed, 19 insertions(+), 20 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index ee20d4c..3504125 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10032,28 +10032,27 @@ SYSCALL_DEFINE5(perf_event_open, goto err_context; /* - * Do not allow to attach to a group in a different - * task or CPU context: + * Make sure we're both events for the same CPU; + * grouping events for different CPUs is broken; since + * you can never concurrently schedule them anyhow. */ - if (move_group) { - /* - * Make sure we're both on the same task, or both - * per-cpu events. - */ - if (group_leader->ctx->task != ctx->task) - goto err_context; + if (group_leader->cpu != event->cpu) + goto err_context; - /* - * Make sure we're both events for the same CPU; - * grouping events for different CPUs is broken; since - * you can never concurrently schedule them anyhow. - */ - if (group_leader->cpu != event->cpu) - goto err_context; - } else { - if (group_leader->ctx != ctx) - goto err_context; - } + /* + * Make sure we're both on the same task, or both + * per-CPU events. + */ + if (group_leader->ctx->task != ctx->task) + goto err_context; + + /* + * Do not allow to attach to a group in a different task + * or CPU context. If we're moving SW events, we'll fix + * this up later, so allow that. + */ + if (!move_group && group_leader->ctx != ctx) + goto err_context; /* * Only a group leader can be exclusive or pinned