From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 174B1C388F9 for ; Mon, 23 Nov 2020 20:34:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CC34D20727 for ; Mon, 23 Nov 2020 20:34:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728866AbgKWUeu (ORCPT ); Mon, 23 Nov 2020 15:34:50 -0500 Received: from mail.kernel.org ([198.145.29.99]:44466 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727448AbgKWUeu (ORCPT ); Mon, 23 Nov 2020 15:34:50 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6E17420715 for ; Mon, 23 Nov 2020 20:34:49 +0000 (UTC) Date: Mon, 23 Nov 2020 15:34:47 -0500 From: Steven Rostedt To: Linux Trace Devel Subject: [PATCH] tracefs utils: Do not free a the buffer on a zero size str_read_file() Message-ID: <20201123153447.2e24c678@gandalf.local.home> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org From: "Steven Rostedt (VMware)" If a file has no size (nothing is read), then str_read_file() frees the buffer and returns zero. The problem is that all callers of str_read_file() uses the buffer supplied if the value returned is not a negative. This causes the freed buffer being used by the callers if the file read existed but had no content. This is apparent when using a copy of the tracefs directory, where some file exist, but have no content, then loading the events would cause a segfault. Signed-off-by: Steven Rostedt (VMware) --- tracefs-utils.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tracefs-utils.c b/tracefs-utils.c index 326b455..690506c 100644 --- a/tracefs-utils.c +++ b/tracefs-utils.c @@ -220,7 +220,7 @@ __hidden int str_read_file(const char *file, char **buffer) } while (r > 0); close(fd); - if (r == 0 && size > 0) { + if (r == 0) { buf[size] = '\0'; *buffer = buf; } else -- 2.25.4