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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 0FD61C2BB1D for ; Tue, 7 Apr 2020 13:10:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D6E6820731 for ; Tue, 7 Apr 2020 13:10:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728783AbgDGNKj (ORCPT ); Tue, 7 Apr 2020 09:10:39 -0400 Received: from mail.parknet.co.jp ([210.171.160.6]:37268 "EHLO mail.parknet.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728640AbgDGNKi (ORCPT ); Tue, 7 Apr 2020 09:10:38 -0400 Received: from ibmpc.myhome.or.jp (server.parknet.ne.jp [210.171.168.39]) by mail.parknet.co.jp (Postfix) with ESMTPSA id C491A12F211; Tue, 7 Apr 2020 22:10:37 +0900 (JST) Received: from devron.myhome.or.jp (foobar@devron.myhome.or.jp [192.168.0.3]) by ibmpc.myhome.or.jp (8.15.2/8.15.2/Debian-18) with ESMTPS id 037DAaWA154643 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 7 Apr 2020 22:10:37 +0900 Received: from devron.myhome.or.jp (foobar@localhost [127.0.0.1]) by devron.myhome.or.jp (8.15.2/8.15.2/Debian-18) with ESMTPS id 037DAaMM906835 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 7 Apr 2020 22:10:36 +0900 Received: (from hirofumi@localhost) by devron.myhome.or.jp (8.15.2/8.15.2/Submit) id 037DAUks906833; Tue, 7 Apr 2020 22:10:30 +0900 From: OGAWA Hirofumi To: Andrew Morton Cc: syzbot , Marco Elver , LKML , syzkaller-bugs , syzkaller , Dmitry Vyukov Subject: [PATCH] fat: Don't allow to mount if the FAT length == 0 Date: Tue, 07 Apr 2020 22:10:30 +0900 Message-ID: <87r1wz8mrd.fsf@mail.parknet.co.jp> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If FAT length == 0, the image doesn't have any data. And it can be the cause of overlapping the root dir and FAT entries. Also Windows treats it as invalid format. Reported-by: syzbot+6f1624f937d9d6911e2d@syzkaller.appspotmail.com Signed-off-by: OGAWA Hirofumi --- fs/fat/inode.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/fat/inode.c b/fs/fat/inode.c index 71946da..bf8e04e 100644 --- a/fs/fat/inode.c 2020-04-07 21:55:27.001147223 +0900 +++ b/fs/fat/inode.c 2020-04-07 22:06:15.164098069 +0900 @@ -1520,6 +1520,12 @@ static int fat_read_bpb(struct super_blo goto out; } + if (bpb->fat_fat_length == 0 && bpb->fat32_length == 0) { + if (!silent) + fat_msg(sb, KERN_ERR, "bogus number of FAT sectors"); + goto out; + } + error = 0; out: _ OGAWA Hirofumi writes: