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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 7E71BC4361B for ; Fri, 18 Dec 2020 05:20:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43CD123A53 for ; Fri, 18 Dec 2020 05:20:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732559AbgLRFUL (ORCPT ); Fri, 18 Dec 2020 00:20:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60442 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731747AbgLRFUK (ORCPT ); Fri, 18 Dec 2020 00:20:10 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 915F8C0617A7 for ; Thu, 17 Dec 2020 21:19:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=Content-Transfer-Encoding:MIME-Version: Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:In-Reply-To:References; bh=oZuF6ObLw2MhepsfeO7KviO77+kjHkMk2gYyhSP9s8E=; b=ismFjqs4KR+eixVDEwUkDCT89B Rz4b+lVUNrDUvnKbXrW032F+JoK7govK3ZFfasiEUl0TUUzFf8d2zpFPxb2gZNfFDPKX5owjNhQKy M1Y+qOAqI71PDiCYQWBoscx5+yEVJP2sEd0YmzBBiHwr3k52prXQadxXntpJD7gbi2YjxBEpki2NS 5sVKOFzHIXhc/Ve5dXKj0g2fnyPUp38ho3EvYMuWLhQagqZQDiERyhL618m3Z/mwwFdH+Lbn52nXx gpRQgMxGdNBaY+bLaL/9kSoo+iaXLxCWaAG7HyFPhAHEcKezUN5M8pzjuPYO8Rho5m59AbHcPopGI 02DlTw/g==; Received: from [2601:1c0:6280:3f0::64ea] (helo=smtpauth.infradead.org) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kq8Ap-0003Kf-Q5; Fri, 18 Dec 2020 05:19:28 +0000 From: Randy Dunlap To: linux-kernel@vger.kernel.org Cc: Randy Dunlap , syzbot+36315852ece4132ec193@syzkaller.appspotmail.com, Dave Kleikamp , jfs-discussion@lists.sourceforge.net Subject: [PATCH] JFS: more checks for invalid superblock Date: Thu, 17 Dec 2020 21:19:20 -0800 Message-Id: <20201218051920.6229-1-rdunlap@infradead.org> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org syzbot is feeding invalid superblock data to JFS for mount testing. JFS does not check several of the fields -- just assumes that they are good since the JFS_MAGIC and version fields are good. In this case (syzbot reproducer), we have s_l2bsize == 0xda0c, pad == 0xf045, and s_state == 0x50, all of which are invalid IMO. Having s_l2bsize == 0xda0c causes this UBSAN warning: UBSAN: shift-out-of-bounds in fs/jfs/jfs_mount.c:373:25 shift exponent -9716 is negative s_l2bsize can be tested for correctness. pad can be tested for non-0 and punted. s_state can be tested for its valid values and punted. Do those 3 tests and if any of them fails, report the superblock as invalid/corrupt and let fsck handle it. With this patch, chkSuper() says this when JFS_DEBUG is enabled: jfs_mount: Mount Failure: superblock is corrupt! Mount JFS Failure: -22 jfs_mount failed w/return code = -22 The obvious problem with this method is that next week there could be another syzbot test that uses different fields for invalid values, this making this like a game of whack-a-mole. syzkaller link: https://syzkaller.appspot.com/bug?extid=36315852ece4132ec193 Reported-by: syzbot+36315852ece4132ec193@syzkaller.appspotmail.com Signed-off-by: Randy Dunlap Cc: Dave Kleikamp Cc: jfs-discussion@lists.sourceforge.net --- fs/jfs/jfs_filsys.h | 1 + fs/jfs/jfs_mount.c | 10 ++++++++++ 2 files changed, 11 insertions(+) --- lnx-510.orig/fs/jfs/jfs_mount.c +++ lnx-510/fs/jfs/jfs_mount.c @@ -37,6 +37,7 @@ #include #include #include +#include #include "jfs_incore.h" #include "jfs_filsys.h" @@ -366,6 +367,15 @@ static int chkSuper(struct super_block * sbi->bsize = bsize; sbi->l2bsize = le16_to_cpu(j_sb->s_l2bsize); + /* check some fields for possible corruption */ + if (sbi->l2bsize != ilog2((u32)bsize) || + j_sb->pad != 0 || + j_sb->s_state > FM_STATE_MAX) { + rc = -EINVAL; + jfs_err("jfs_mount: Mount Failure: superblock is corrupt!"); + goto out; + } + /* * For now, ignore s_pbsize, l2bfactor. All I/O going through buffer * cache. --- lnx-510.orig/fs/jfs/jfs_filsys.h +++ lnx-510/fs/jfs/jfs_filsys.h @@ -268,5 +268,6 @@ * fsck() must be run to repair */ #define FM_EXTENDFS 0x00000008 /* file system extendfs() in progress */ +#define FM_STATE_MAX 0x0000000f /* max value of s_state */ #endif /* _H_JFS_FILSYS */