From patchwork Tue Sep 12 18:07:02 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Beau Belgrave X-Patchwork-Id: 13382022 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 2C65BEE3F00 for ; Tue, 12 Sep 2023 18:07:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237304AbjILSHQ (ORCPT ); Tue, 12 Sep 2023 14:07:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48558 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237172AbjILSHP (ORCPT ); Tue, 12 Sep 2023 14:07:15 -0400 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 472CB10D8; Tue, 12 Sep 2023 11:07:11 -0700 (PDT) Received: from localhost.localdomain (unknown [4.155.48.112]) by linux.microsoft.com (Postfix) with ESMTPSA id C6DE2212BC1A; Tue, 12 Sep 2023 11:07:10 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com C6DE2212BC1A DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1694542030; bh=pwgfnQGdYQ7dhrASDB16knk3pMkjAyqpomjeERDUJlc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OwdP8ZmyOXqIQfJ+1KExC6cxFh7aklIGehuRzQTeGUWv5VOHkNXtB96OAGHtHS53w /PCYLQjajPdGfrPCKG+oLLGDRx7/EQuePqOlyNVugLrja72QynpBgthlz4TY3LE28I P11sDV/9GOvdj7jGJ14B8olkkoGWRECPfRb2oNJI= From: Beau Belgrave To: rostedt@goodmis.org, mhiramat@kernel.org Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, ast@kernel.org, dcook@linux.microsoft.com Subject: [PATCH v2 1/3] tracing/user_events: Allow events to persist for perfmon_capable users Date: Tue, 12 Sep 2023 18:07:02 +0000 Message-Id: <20230912180704.1284-2-beaub@linux.microsoft.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230912180704.1284-1-beaub@linux.microsoft.com> References: <20230912180704.1284-1-beaub@linux.microsoft.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org There are several scenarios that have come up where having a user_event persist even if the process that registered it exits. The main one is having a daemon create events on bootup that shouldn't get deleted if the daemon has to exit or reload. Another is within OpenTelemetry exporters, they wish to potentially check if a user_event exists on the system to determine if exporting the data out should occur. The user_event in this case must exist even in the absence of the owning process running (such as the above daemon case). Expose the previously internal flag USER_EVENT_REG_PERSIST to user processes. Upon register or delete of events with this flag, ensure the user is perfmon_capable to prevent random user processes with access to tracefs from creating events that persist after exit. Signed-off-by: Beau Belgrave --- include/uapi/linux/user_events.h | 11 +++++++++- kernel/trace/trace_events_user.c | 36 +++++++++++++++++++------------- 2 files changed, 32 insertions(+), 15 deletions(-) diff --git a/include/uapi/linux/user_events.h b/include/uapi/linux/user_events.h index 2984aae4a2b4..f74f3aedd49c 100644 --- a/include/uapi/linux/user_events.h +++ b/include/uapi/linux/user_events.h @@ -17,6 +17,15 @@ /* Create dynamic location entry within a 32-bit value */ #define DYN_LOC(offset, size) ((size) << 16 | (offset)) +/* List of supported registration flags */ +enum user_reg_flag { + /* Event will not delete upon last reference closing */ + USER_EVENT_REG_PERSIST = 1U << 0, + + /* This value or above is currently non-ABI */ + USER_EVENT_REG_MAX = 1U << 1, +}; + /* * Describes an event registration and stores the results of the registration. * This structure is passed to the DIAG_IOCSREG ioctl, callers at a minimum @@ -33,7 +42,7 @@ struct user_reg { /* Input: Enable size in bytes at address */ __u8 enable_size; - /* Input: Flags for future use, set to 0 */ + /* Input: Flags to use, if any */ __u16 flags; /* Input: Address to update when enabled */ diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c index 6f046650e527..e3f2b8d72e01 100644 --- a/kernel/trace/trace_events_user.c +++ b/kernel/trace/trace_events_user.c @@ -49,18 +49,6 @@ #define EVENT_STATUS_PERF BIT(1) #define EVENT_STATUS_OTHER BIT(7) -/* - * User register flags are not allowed yet, keep them here until we are - * ready to expose them out to the user ABI. - */ -enum user_reg_flag { - /* Event will not delete upon last reference closing */ - USER_EVENT_REG_PERSIST = 1U << 0, - - /* This value or above is currently non-ABI */ - USER_EVENT_REG_MAX = 1U << 1, -}; - /* * Stores the system name, tables, and locks for a group of events. This * allows isolation for events by various means. @@ -191,6 +179,17 @@ static u32 user_event_key(char *name) return jhash(name, strlen(name), 0); } +static bool user_event_capable(u16 reg_flags) +{ + /* Persistent events require CAP_PERFMON / CAP_SYS_ADMIN */ + if (reg_flags & USER_EVENT_REG_PERSIST) { + if (!perfmon_capable()) + return false; + } + + return true; +} + static struct user_event *user_event_get(struct user_event *user) { refcount_inc(&user->refcnt); @@ -1773,6 +1772,9 @@ static int user_event_free(struct dyn_event *ev) if (!user_event_last_ref(user)) return -EBUSY; + if (!user_event_capable(user->reg_flags)) + return -EPERM; + return destroy_user_event(user); } @@ -1888,10 +1890,13 @@ static int user_event_parse(struct user_event_group *group, char *name, int argc = 0; char **argv; - /* User register flags are not ready yet */ - if (reg_flags != 0 || flags != NULL) + /* Currently don't support any text based flags */ + if (flags != NULL) return -EINVAL; + if (!user_event_capable(reg_flags)) + return -EPERM; + /* Prevent dyn_event from racing */ mutex_lock(&event_mutex); user = find_user_event(group, name, &key); @@ -2024,6 +2029,9 @@ static int delete_user_event(struct user_event_group *group, char *name) if (!user_event_last_ref(user)) return -EBUSY; + if (!user_event_capable(user->reg_flags)) + return -EPERM; + return destroy_user_event(user); }