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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 9F947C282C2 for ; Wed, 13 Feb 2019 17:29:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7AA1720838 for ; Wed, 13 Feb 2019 17:29:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393035AbfBMR3p (ORCPT ); Wed, 13 Feb 2019 12:29:45 -0500 Received: from mail.parknet.co.jp ([210.171.160.6]:53258 "EHLO mail.parknet.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388566AbfBMR3p (ORCPT ); Wed, 13 Feb 2019 12:29:45 -0500 Received: from ibmpc.myhome.or.jp (server.parknet.ne.jp [210.171.168.39]) by mail.parknet.co.jp (Postfix) with ESMTPSA id 642231B408E; Thu, 14 Feb 2019 02:29:44 +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-12) with ESMTPS id x1DHThhl020052 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Thu, 14 Feb 2019 02:29:44 +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-12) with ESMTPS id x1DHTggU013110 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Thu, 14 Feb 2019 02:29:42 +0900 Received: (from hirofumi@localhost) by devron.myhome.or.jp (8.15.2/8.15.2/Submit) id x1DHTgiP013109; Thu, 14 Feb 2019 02:29:42 +0900 From: OGAWA Hirofumi To: Matteo Croce Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Timothy Redaelli Subject: Re: [PATCH v3] vfat: don't read garbage after last dirent References: <20190201001408.7453-1-mcroce@redhat.com> Date: Thu, 14 Feb 2019 02:29:42 +0900 In-Reply-To: <20190201001408.7453-1-mcroce@redhat.com> (Matteo Croce's message of "Fri, 1 Feb 2019 01:14:08 +0100") Message-ID: <87sgwr61h5.fsf@mail.parknet.co.jp> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Matteo Croce writes: > The FAT32 File System Specification[1] states that: > > If DIR_Name[0] == 0x00, then the directory entry is free, and there > are no allocated directory entries after this one. > > The special 0 value, indicates to FAT file system driver code that > the rest of the entries in this directory do not need to be examined > because they are all free. > > This is not enforced by Linux, and is possible to read garbage if not > all dirents after the last one are filled with zeroes. > > [1] http://download.microsoft.com/download/1/6/1/161ba512-40e2-4cc9-843a-923143f3456c/fatgen103.doc Tested some, and this patch seems to be not working. First fat_readdir() exits by zero dir entry, but dir pos is updated to next position, then second fat_readdir() continue with previous dir pos and will read beyond zero dir entry. So, maybe, we are better move down the zero dir entry handling into fat_get_entry(), instead of copying several places. But like you know, we would like to skip the zero dir entry only if read/search operation. Maybe, adding flag to fat_get_entry() and use it, or adding small wrapper? And in read/search case, we should not update *pos if hit the zero dir entry. I'm not testing the above actually though, we would need such. Thanks. > Reported-by: Timothy Redaelli > Signed-off-by: Matteo Croce > --- > fs/fat/dir.c | 20 ++++++++++++-------- > 1 file changed, 12 insertions(+), 8 deletions(-) > > diff --git a/fs/fat/dir.c b/fs/fat/dir.c > index 9d01db37183f..d919a1ee519c 100644 > --- a/fs/fat/dir.c > +++ b/fs/fat/dir.c > @@ -314,7 +314,7 @@ static int fat_parse_long(struct inode *dir, loff_t *pos, > > if (ds->id & 0x40) > (*unicode)[offset + 13] = 0; > - if (fat_get_entry(dir, pos, bh, de) < 0) > + if (fat_get_entry(dir, pos, bh, de) < 0 || !(*de)->name[0]) > return PARSE_EOF; > if (slot == 0) > break; > @@ -476,7 +476,8 @@ int fat_search_long(struct inode *inode, const unsigned char *name, > > err = -ENOENT; > while (1) { > - if (fat_get_entry(inode, &cpos, &bh, &de) == -1) > + if (fat_get_entry(inode, &cpos, &bh, &de) == -1 || > + !de->name[0]) > goto end_of_dir; > parse_record: > nr_slots = 0; > @@ -588,7 +589,7 @@ static int __fat_readdir(struct inode *inode, struct file *file, > > bh = NULL; > get_new: > - if (fat_get_entry(inode, &cpos, &bh, &de) == -1) > + if (fat_get_entry(inode, &cpos, &bh, &de) == -1 || !de->name[0]) > goto end_of_dir; > parse_record: > nr_slots = 0; > @@ -898,7 +899,8 @@ int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh, > loff_t offset = 0; > > *de = NULL; > - while (fat_get_short_entry(dir, &offset, bh, de) >= 0) { > + while (fat_get_short_entry(dir, &offset, bh, de) >= 0 && > + (*de)->name[0]) { > if (!strncmp((*de)->name, MSDOS_DOTDOT, MSDOS_NAME)) > return 0; > } > @@ -916,7 +918,8 @@ int fat_dir_empty(struct inode *dir) > > bh = NULL; > cpos = 0; > - while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0) { > + while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0 && > + de->name[0]) { > if (strncmp(de->name, MSDOS_DOT , MSDOS_NAME) && > strncmp(de->name, MSDOS_DOTDOT, MSDOS_NAME)) { > result = -ENOTEMPTY; > @@ -941,7 +944,8 @@ int fat_subdirs(struct inode *dir) > > bh = NULL; > cpos = 0; > - while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0) { > + while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0 && > + de->name[0]) { > if (de->attr & ATTR_DIR) > count++; > } > @@ -961,7 +965,7 @@ int fat_scan(struct inode *dir, const unsigned char *name, > sinfo->slot_off = 0; > sinfo->bh = NULL; > while (fat_get_short_entry(dir, &sinfo->slot_off, &sinfo->bh, > - &sinfo->de) >= 0) { > + &sinfo->de) >= 0 && sinfo->de->name[0]) { > if (!strncmp(sinfo->de->name, name, MSDOS_NAME)) { > sinfo->slot_off -= sizeof(*sinfo->de); > sinfo->nr_slots = 1; > @@ -985,7 +989,7 @@ int fat_scan_logstart(struct inode *dir, int i_logstart, > sinfo->slot_off = 0; > sinfo->bh = NULL; > while (fat_get_short_entry(dir, &sinfo->slot_off, &sinfo->bh, > - &sinfo->de) >= 0) { > + &sinfo->de) >= 0 && sinfo->de->name[0]) { > if (fat_get_start(MSDOS_SB(sb), sinfo->de) == i_logstart) { > sinfo->slot_off -= sizeof(*sinfo->de); > sinfo->nr_slots = 1; -- OGAWA Hirofumi