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=-20.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 C55D0C433EF for ; Mon, 20 Sep 2021 18:11:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AFDF061A0A for ; Mon, 20 Sep 2021 18:11:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351074AbhITSMt (ORCPT ); Mon, 20 Sep 2021 14:12:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:60800 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358605AbhITSHI (ORCPT ); Mon, 20 Sep 2021 14:07:08 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9FC8D6324F; Mon, 20 Sep 2021 17:18:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1632158293; bh=0bxMqghMWE8jYyhwodguChsinCuVvW/DSK+nOv02lts=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1qyrO2qTE0STPQ11Lxt6e2EbEPgREp4M6aEBsm9RtpxvvniFVEYz1MnWwBKD0WGc0 M7dqDFhqH1TFEnhjaO2faQ7ai/6uB8h2JdLQfSsMnP48cSUHiZGRfwuouLVARMZGvu 8KN50XCRsJCHqHj5yWscl0U3/kPzQ6tEYm/1I++g= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yangtao Li , Chao Yu , Jaegeuk Kim , Sasha Levin Subject: [PATCH 5.4 047/260] f2fs: reduce the scope of setting fsck tag when de->name_len is zero Date: Mon, 20 Sep 2021 18:41:05 +0200 Message-Id: <20210920163932.709960824@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210920163931.123590023@linuxfoundation.org> References: <20210920163931.123590023@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yangtao Li [ Upstream commit d4bf15a7ce172d186d400d606adf4f34a59130d6 ] I recently found a case where de->name_len is 0 in f2fs_fill_dentries() easily reproduced, and finally set the fsck flag. Thread A Thread B - f2fs_readdir - f2fs_read_inline_dir - ctx->pos = d.max - f2fs_add_dentry - f2fs_add_inline_entry - do_convert_inline_dir - f2fs_add_regular_entry - f2fs_readdir - f2fs_fill_dentries - set_sbi_flag(sbi, SBI_NEED_FSCK) Process A opens the folder, and has been reading without closing it. During this period, Process B created a file under the folder (occupying multiple f2fs_dir_entry, exceeding the d.max of the inline dir). After creation, process A uses the d.max of inline dir to read it again, and it will read that de->name_len is 0. And Chao pointed out that w/o inline conversion, the race condition still can happen as below: dir_entry1: A dir_entry2: B dir_entry3: C free slot: _ ctx->pos: ^ Thread A is traversing directory, ctx-pos moves to below position after readdir() by thread A: AAAABBBB___ ^ Then thread B delete dir_entry2, and create dir_entry3. Thread A calls readdir() to lookup dirents starting from middle of new dirent slots as below: AAAACCCCCC_ ^ In these scenarios, the file system is not damaged, and it's hard to avoid it. But we can bypass tagging FSCK flag if: a) bit_pos (:= ctx->pos % d->max) is non-zero and b) before bit_pos moves to first valid dir_entry. Fixes: ddf06b753a85 ("f2fs: fix to trigger fsck if dirent.name_len is zero") Signed-off-by: Yangtao Li [Chao: clean up description] Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim Signed-off-by: Sasha Levin --- fs/f2fs/dir.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index 7b3fbfe68f8c..99c4a868d73b 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -892,6 +892,7 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d, struct f2fs_sb_info *sbi = F2FS_I_SB(d->inode); struct blk_plug plug; bool readdir_ra = sbi->readdir_ra == 1; + bool found_valid_dirent = false; int err = 0; bit_pos = ((unsigned long)ctx->pos % d->max); @@ -906,13 +907,15 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d, de = &d->dentry[bit_pos]; if (de->name_len == 0) { + if (found_valid_dirent || !bit_pos) { + printk_ratelimited( + "%sF2FS-fs (%s): invalid namelen(0), ino:%u, run fsck to fix.", + KERN_WARNING, sbi->sb->s_id, + le32_to_cpu(de->ino)); + set_sbi_flag(sbi, SBI_NEED_FSCK); + } bit_pos++; ctx->pos = start_pos + bit_pos; - printk_ratelimited( - "%sF2FS-fs (%s): invalid namelen(0), ino:%u, run fsck to fix.", - KERN_WARNING, sbi->sb->s_id, - le32_to_cpu(de->ino)); - set_sbi_flag(sbi, SBI_NEED_FSCK); continue; } @@ -955,6 +958,7 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d, f2fs_ra_node_page(sbi, le32_to_cpu(de->ino)); ctx->pos = start_pos + bit_pos; + found_valid_dirent = true; } out: if (readdir_ra) -- 2.30.2