From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 24 Jan 2002 19:35:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 24 Jan 2002 19:35:16 -0500 Received: from harpo.it.uu.se ([130.238.12.34]:39811 "EHLO harpo.it.uu.se") by vger.kernel.org with ESMTP id ; Thu, 24 Jan 2002 19:35:04 -0500 Date: Fri, 25 Jan 2002 01:35:02 +0100 (MET) From: Mikael Pettersson Message-Id: <200201250035.BAA27730@harpo.it.uu.se> To: torvalds@transmeta.com, viro@math.psu.edu Subject: [PATCH] ext2 FS corruption in 2.5.3-pre[3-5] Cc: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Al & Linus, There is a file system corruption problem in 2.5.3-pre[3-5], caused by leaking uninitialised memory to in-core and later on-disk inodes. I can easily observe the problem by creating lots of files in an ext2 FS, reboot to single-user, and fsck the ext2 FS partition. fsck will then give a lot of warnings about: "i_fsize for inode NNN (...) is XX, should be zero" where XX is a random non-zero 8-bit number. I traced it to the pre2->pre3 transition, which contains: > - Al Viro: VFS inode allocation moved down to filesystem, trim inodes When FS-specific data was stored in inode->u, that data was cleared by the memset() in fs/inode.c:alloc_inode(). The FS didn't have to bother. Since -pre3, ext2 (and perhaps other FSs, I haven't checked) uses an in-core inode layout consisting of an FS-specific head followed by the generic inode. ext2 allocates these in fs/ext2/super.c:ext2_alloc_inode(), but doesn't clear the ext2-specific fields. fs/inode.c:alloc_inode() neither knows about these fields nor clears them, so the ext2-specific data remains uninitialised when the new inode is returned for use. Ouch. The patch below fixes this by adding the missing memset() to fs/ext2/super.c:ext2_alloc_inode(). Works fine over here. /Mikael --- linux-2.5.3-pre5/fs/ext2/super.c.~1~ Fri Jan 25 00:03:58 2002 +++ linux-2.5.3-pre5/fs/ext2/super.c Fri Jan 25 00:35:12 2002 @@ -155,6 +155,7 @@ ei = (struct ext2_inode_info *)kmem_cache_alloc(ext2_inode_cachep, SLAB_KERNEL); if (!ei) return NULL; + memset(ei, 0, offsetof(struct ext2_inode_info, vfs_inode)); return &ei->vfs_inode; }