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=-10.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 16F68C433E1 for ; Mon, 29 Jun 2020 19:12:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F10A7206E2 for ; Mon, 29 Jun 2020 19:12:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730839AbgF2TME (ORCPT ); Mon, 29 Jun 2020 15:12:04 -0400 Received: from mslow2.mail.gandi.net ([217.70.178.242]:46628 "EHLO mslow2.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730529AbgF2TMC (ORCPT ); Mon, 29 Jun 2020 15:12:02 -0400 X-Greylist: delayed 1030 seconds by postgrey-1.27 at vger.kernel.org; Mon, 29 Jun 2020 15:12:01 EDT Received: from relay9-d.mail.gandi.net (unknown [217.70.183.199]) by mslow2.mail.gandi.net (Postfix) with ESMTP id D75E93AB679 for ; Mon, 29 Jun 2020 14:00:33 +0000 (UTC) X-Originating-IP: 84.44.14.226 Received: from nexussix.ar.arcelik (unknown [84.44.14.226]) (Authenticated sender: cengiz@kernel.wtf) by relay9-d.mail.gandi.net (Postfix) with ESMTPSA id 53A10FF80E; Mon, 29 Jun 2020 14:00:09 +0000 (UTC) From: Cengiz Can To: Jason Wessel , Daniel Thompson , Douglas Anderson Cc: kgdb-bugreport@lists.sourceforge.net, linux-kernel@vger.kernel.org, Sumit Garg , Petr Mladek , Andy Shevchenko , Cengiz Can Subject: [PATCH] kdb: prevent possible null deref in kdb_msg_write Date: Mon, 29 Jun 2020 16:59:24 +0300 Message-Id: <20200629135923.14912-1-cengiz@kernel.wtf> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org `kdb_msg_write` operates on a global `struct kgdb_io *` called `dbg_io_ops`. Although it is initialized in `debug_core.c`, there's a null check in `kdb_msg_write` which implies that it can be null whenever we dereference it in this function call. Coverity scanner caught this as CID 1465042. I have modified the function to bail out if `dbg_io_ops` is not properly initialized. Signed-off-by: Cengiz Can --- kernel/debug/kdb/kdb_io.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 683a799618ad..85e579812458 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -549,14 +549,15 @@ static void kdb_msg_write(const char *msg, int msg_len) if (msg_len == 0) return; - if (dbg_io_ops) { - const char *cp = msg; - int len = msg_len; + if (!dbg_io_ops) + return; - while (len--) { - dbg_io_ops->write_char(*cp); - cp++; - } + const char *cp = msg; + int len = msg_len; + + while (len--) { + dbg_io_ops->write_char(*cp); + cp++; } for_each_console(c) { -- 2.27.0