From patchwork Wed Mar 23 14:39:12 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 12789817 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 D2311C433EF for ; Wed, 23 Mar 2022 14:39:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244316AbiCWOkp (ORCPT ); Wed, 23 Mar 2022 10:40:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240637AbiCWOko (ORCPT ); Wed, 23 Mar 2022 10:40:44 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5BCBC574B2; Wed, 23 Mar 2022 07:39:15 -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 E934761725; Wed, 23 Mar 2022 14:39:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FED4C340E8; Wed, 23 Mar 2022 14:39:13 +0000 (UTC) Date: Wed, 23 Mar 2022 10:39:12 -0400 From: Steven Rostedt To: LKML Cc: Ingo Molnar , Andrew Morton , linux-xfs@vger.kernel.org, Brian Foster Subject: [PATCH] tracing: Have trace event string test handle zero length strings Message-ID: <20220323103912.097ad3a8@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org From: "Steven Rostedt (Google)" If a trace event has in its TP_printk(): "%*.s", len, len ? __get_str(string) : NULL It is perfectly valid if len is zero and passing in the NULL. Unfortunately, the runtime string check at time of reading the trace sees the NULL and flags it as a bad string and produces a WARN_ON(). Handle this case by passing into the test function if the format has an asterisk (star) and if so, if the length is zero, then mark it as safe. Link: https://lore.kernel.org/all/YjsWzuw5FbWPrdqq@bfoster/ Cc: stable@vger.kernel.org Reported-by: Brian Foster Fixes: 9a6944fee68e2 ("tracing: Add a verifier to check string pointers for trace events") Signed-off-by: Steven Rostedt (Google) Tested-by: Brian Foster --- kernel/trace/trace.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index eb44418574f9..96265a717ca4 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3663,12 +3663,17 @@ static char *trace_iter_expand_format(struct trace_iterator *iter) } /* Returns true if the string is safe to dereference from an event */ -static bool trace_safe_str(struct trace_iterator *iter, const char *str) +static bool trace_safe_str(struct trace_iterator *iter, const char *str, + bool star, int len) { unsigned long addr = (unsigned long)str; struct trace_event *trace_event; struct trace_event_call *event; + /* Ignore strings with no length */ + if (star && !len) + return true; + /* OK if part of the event data */ if ((addr >= (unsigned long)iter->ent) && (addr < (unsigned long)iter->ent + iter->ent_size)) @@ -3854,7 +3859,7 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt, * instead. See samples/trace_events/trace-events-sample.h * for reference. */ - if (WARN_ONCE(!trace_safe_str(iter, str), + if (WARN_ONCE(!trace_safe_str(iter, str, star, len), "fmt: '%s' current_buffer: '%s'", fmt, show_buffer(&iter->seq))) { int ret;