From patchwork Fri Jan 20 23:05:18 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Beau Belgrave X-Patchwork-Id: 13110666 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5C3CC27C76 for ; Fri, 20 Jan 2023 23:05:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230305AbjATXFv (ORCPT ); Fri, 20 Jan 2023 18:05:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45744 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230223AbjATXFo (ORCPT ); Fri, 20 Jan 2023 18:05:44 -0500 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 0D9D56C110; Fri, 20 Jan 2023 15:05:28 -0800 (PST) Received: from W11-BEAU-MD.localdomain (unknown [76.135.27.212]) by linux.microsoft.com (Postfix) with ESMTPSA id AB47320E1A6B; Fri, 20 Jan 2023 15:05:27 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com AB47320E1A6B DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1674255927; bh=I/N19C63THCRBfckR+N4mJDWmIQC1iuXco7+RGR9L6U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SK5dRfzR4/nxY3YgaP7m5idhYDRxWsW49m02gGcehSA/py9fnkwc5f7AmXruNj+K3 dfGAQHrv+DuYcuV+TnRf0/V1kAwpj/trI5O6mEpVwDJaInu1Il1pRdOfje9mRt4Ld1 HL2iirA5RWNTU8U6aN+ty0QD3qtQN1kZzTgl2VuY= From: Beau Belgrave To: rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, dcook@linux.microsoft.com, alanau@linux.microsoft.com, brauner@kernel.org, akpm@linux-foundation.org Cc: linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v7 11/11] tracing/user_events: Limit global user_event count Date: Fri, 20 Jan 2023 15:05:18 -0800 Message-Id: <20230120230518.17697-12-beaub@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230120230518.17697-1-beaub@linux.microsoft.com> References: <20230120230518.17697-1-beaub@linux.microsoft.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org Operators want to be able to ensure enough tracepoints exist on the system for kernel components as well as for user components. Since there are only up to 64K events, by default allow up to half to be used by user events. Add a boot parameter (user_events_max=%d) and a kernel sysctl parameter (kernel.user_events_max) to set a global limit that is honored among all groups on the system. This ensures hard limits can be setup to prevent user processes from consuming all event IDs on the system. Signed-off-by: Beau Belgrave --- kernel/trace/trace_events_user.c | 59 ++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c index 222f2eb59c7c..6a5ebe243999 100644 --- a/kernel/trace/trace_events_user.c +++ b/kernel/trace/trace_events_user.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include "trace.h" #include "trace_dynevent.h" @@ -61,6 +62,12 @@ struct user_event_group { /* Group for init_user_ns mapping, top-most group */ static struct user_event_group *init_group; +/* Max allowed events for the whole system */ +static unsigned int max_user_events = 32768; + +/* Current number of events on the whole system */ +static unsigned int current_user_events; + /* * Stores per-event properties, as users register events * within a file a user_event might be created if it does not @@ -1241,6 +1248,8 @@ static int destroy_user_event(struct user_event *user) { int ret = 0; + lockdep_assert_held(&event_mutex); + /* Must destroy fields before call removal */ user_event_destroy_fields(user); @@ -1257,6 +1266,11 @@ static int destroy_user_event(struct user_event *user) kfree(EVENT_NAME(user)); kfree(user); + if (current_user_events > 0) + current_user_events--; + else + pr_alert("BUG: Bad current_user_events\n"); + return ret; } @@ -1744,6 +1758,11 @@ static int user_event_parse(struct user_event_group *group, char *name, mutex_lock(&event_mutex); + if (current_user_events >= max_user_events) { + ret = -EMFILE; + goto put_user_lock; + } + ret = user_event_trace_register(user); if (ret) @@ -1755,6 +1774,7 @@ static int user_event_parse(struct user_event_group *group, char *name, dyn_event_init(&user->devent, &user_event_dops); dyn_event_add(&user->devent, &user->call); hash_add(group->register_table, &user->node, key); + current_user_events++; mutex_unlock(&event_mutex); @@ -2386,6 +2406,43 @@ static int create_user_tracefs(void) return -ENODEV; } +static int __init set_max_user_events(char *str) +{ + if (!str) + return 0; + + if (kstrtouint(str, 0, &max_user_events)) + return 0; + + return 1; +} +__setup("user_events_max=", set_max_user_events); + +static int set_max_user_events_sysctl(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + int ret; + + mutex_lock(&event_mutex); + + ret = proc_douintvec(table, write, buffer, lenp, ppos); + + mutex_unlock(&event_mutex); + + return ret; +} + +static struct ctl_table user_event_sysctls[] = { + { + .procname = "user_events_max", + .data = &max_user_events, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = set_max_user_events_sysctl, + }, + {} +}; + static int __init trace_events_user_init(void) { int ret; @@ -2415,6 +2472,8 @@ static int __init trace_events_user_init(void) if (dyn_event_register(&user_event_dops)) pr_warn("user_events could not register with dyn_events\n"); + register_sysctl_init("kernel", user_event_sysctls); + return 0; }