From patchwork Tue Apr 5 07:31:21 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 557282 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 EF554C433F5 for ; Tue, 5 Apr 2022 10:28:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355762AbiDEKV4 (ORCPT ); Tue, 5 Apr 2022 06:21:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37586 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347723AbiDEJ2M (ORCPT ); Tue, 5 Apr 2022 05:28:12 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 89E62DF4B6; Tue, 5 Apr 2022 02:15:37 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A3F6C61654; Tue, 5 Apr 2022 09:15:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ABA7BC385A2; Tue, 5 Apr 2022 09:15:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649150136; bh=vnpu9QTCzpmy20Jhz1m5rSkro66moiw7kneSHf7UJ3U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uNCVsokMUh+zqA6ggjrUaCevEvKbVRfEb44LmGoZeA95GLk8cXMziQljETg5F8UUQ GIOvL1QxtpJJuNkUUnOOxNJcP+R9nnd3tTY0JV30D7VSECygWmZzfS2w9W+fJ0WYZB skHRXBtmODM6YvvgjfW6xBruG5eTkrVEimNHQzeE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Marc Zyngier , Sven Schnelle , "Steven Rostedt (Google)" Subject: [PATCH 5.16 0968/1017] tracing: Have type enum modifications copy the strings Date: Tue, 5 Apr 2022 09:31:21 +0200 Message-Id: <20220405070422.939029623@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405070354.155796697@linuxfoundation.org> References: <20220405070354.155796697@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Steven Rostedt (Google) commit 795301d3c28996219d555023ac6863401b6076bc upstream. When an enum is used in the visible parts of a trace event that is exported to user space, the user space applications like perf and trace-cmd do not have a way to know what the value of the enum is. To solve this, at boot up (or module load) the printk formats are modified to replace the enum with their numeric value in the string output. Array fields of the event are defined by [] in the type portion of the format file so that the user space parsers can correctly parse the array into the appropriate size chunks. But in some trace events, an enum is used in defining the size of the array, which once again breaks the parsing of user space tooling. This was solved the same way as the print formats were, but it modified the type strings of the trace event. This caused crashes in some architectures because, as supposed to the print string, is a const string value. This was not detected on x86, as it appears that const strings are still writable (at least in boot up), but other architectures this is not the case, and writing to a const string will cause a kernel fault. To fix this, use kstrdup() to copy the type before modifying it. If the trace event is for the core kernel there's no need to free it because the string will be in use for the life of the machine being on line. For modules, create a link list to store all the strings being allocated for modules and when the module is removed, free them. Link: https://lore.kernel.org/all/yt9dr1706b4i.fsf@linux.ibm.com/ Link: https://lkml.kernel.org/r/20220318153432.3984b871@gandalf.local.home Tested-by: Marc Zyngier Tested-by: Sven Schnelle Reported-by: Sven Schnelle Fixes: b3bc8547d3be ("tracing: Have TRACE_DEFINE_ENUM affect trace event types as well") Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_events.c | 62 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 61 insertions(+), 1 deletion(-) --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -40,6 +40,14 @@ static LIST_HEAD(ftrace_generic_fields); static LIST_HEAD(ftrace_common_fields); static bool eventdir_initialized; +static LIST_HEAD(module_strings); + +struct module_string { + struct list_head next; + struct module *module; + char *str; +}; + #define GFP_TRACE (GFP_KERNEL | __GFP_ZERO) static struct kmem_cache *field_cachep; @@ -2637,14 +2645,40 @@ static void update_event_printk(struct t } } +static void add_str_to_module(struct module *module, char *str) +{ + struct module_string *modstr; + + modstr = kmalloc(sizeof(*modstr), GFP_KERNEL); + + /* + * If we failed to allocate memory here, then we'll just + * let the str memory leak when the module is removed. + * If this fails to allocate, there's worse problems than + * a leaked string on module removal. + */ + if (WARN_ON_ONCE(!modstr)) + return; + + modstr->module = module; + modstr->str = str; + + list_add(&modstr->next, &module_strings); +} + static void update_event_fields(struct trace_event_call *call, struct trace_eval_map *map) { struct ftrace_event_field *field; struct list_head *head; char *ptr; + char *str; int len = strlen(map->eval_string); + /* Dynamic events should never have field maps */ + if (WARN_ON_ONCE(call->flags & TRACE_EVENT_FL_DYNAMIC)) + return; + head = trace_get_fields(call); list_for_each_entry(field, head, link) { ptr = strchr(field->type, '['); @@ -2658,9 +2692,26 @@ static void update_event_fields(struct t if (strncmp(map->eval_string, ptr, len) != 0) continue; + str = kstrdup(field->type, GFP_KERNEL); + if (WARN_ON_ONCE(!str)) + return; + ptr = str + (ptr - field->type); ptr = eval_replace(ptr, map, len); /* enum/sizeof string smaller than value */ - WARN_ON_ONCE(!ptr); + if (WARN_ON_ONCE(!ptr)) { + kfree(str); + continue; + } + + /* + * If the event is part of a module, then we need to free the string + * when the module is removed. Otherwise, it will stay allocated + * until a reboot. + */ + if (call->module) + add_str_to_module(call->module, str); + + field->type = str; } } @@ -2885,6 +2936,7 @@ static void trace_module_add_events(stru static void trace_module_remove_events(struct module *mod) { struct trace_event_call *call, *p; + struct module_string *modstr, *m; down_write(&trace_event_sem); list_for_each_entry_safe(call, p, &ftrace_events, list) { @@ -2893,6 +2945,14 @@ static void trace_module_remove_events(s if (call->module == mod) __trace_remove_event_call(call); } + /* Check for any strings allocade for this module */ + list_for_each_entry_safe(modstr, m, &module_strings, next) { + if (modstr->module != mod) + continue; + list_del(&modstr->next); + kfree(modstr->str); + kfree(modstr); + } up_write(&trace_event_sem); /*