From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793214329; b=w06lHH+ptHC9MULPBMbFDje0hvbSpmXc0Di+VE83cHh0PsuJ2nrStknw7aIPlrmWymyg V3UmCp/kNpgaV3m/fCB+Oe2FgXPEACk0r8EV9x0cknQHhMMZEU6UFN/UKnQVXJQ6S4ayq B2owjcoa/EzGckoihvHY0ObfDstbj0fEWqZlDgwadVDRQFZ2zeMW22crsrvNzjUg0S+hQ L7nrc0Y8xAJfLPXSHO6enogSli3VJ1LN9vyBEzTYdc5B+LhkTy1jwCNpmztJ0u9w04Gnn lntn0cL9wdKmheJk+PmT9SXdXOI0IkN0u2ghaciiyLA49vBFBYbkC2r5gtHFAdrUeQg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793214329; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=nGmWgZDkRZRVGBAg0qbGNuzp1thibgbTHpAqgIJDkBA=; b=N6in790kEGMbLEHKYwFYcer9r1B5itstRSpeY84voZ875VxL9fgZ6BoUL3yxaC0us29h VsTpbU1Q3ZSPGrt3Gd3Kx3MqY+3d6wTIHvpJ0gmetCc55VIty3HPCmlFyu4anDWbfWwvV 7eZQXy0KlogslMaCh4112SholRQOEvn6oOIhfOTgGQe7JCA+wTImtp8wgylFxHYJkXSt4 WtRrdbDeP2EYCxUSVS68XcCu3JcXd7wddsIHesjqjUaqDFEAZ1s9+ldC5LsFfgAWA5cK2 YDr7rydr409wPHEewkuTdTYXiscyiArtR9EYZ8SE+XzumuymW18BvT0CmfrfHnCSSbg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=ylG5hO58; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0ED34606A322; Wed, 28 Oct 2026 19:05:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=ylG5hO58 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F14E1F01825; Wed, 28 Oct 2026 19:05:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793214328; bh=nGmWgZDkRZRVGBAg0qbGNuzp1thibgbTHpAqgIJDkBA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ylG5hO587dCIkDsttVbDwFdWzNEkmNn4ilW0JrI9ssFSn2baqIpqw7x2dZS3oFypv Z2Cr7TjWjIYTxebZQq6D/rh20UUf4fC6vCjkBHuAqCdRZy8RZd6mIiHCpulVEiM2AD O3RPF2msqKO/p/Pu7VfGyypPEjpkpi94snfNTWds= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yuezhang Mo , Namjae Jeon , Sasha Levin Subject: [PATCH 6.1 0821/1887] exfat: add cluster chain loop check for dir Date: Wed, 28 Oct 2026 17:48:37 +0100 Message-ID: <20261028170518.109452552@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170459.200466217@linuxfoundation.org> References: <20261028170459.200466217@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yuezhang Mo [ Upstream commit 99f9a97dce39ad413c39b92c90393bbd6778f3fd ] An infinite loop may occur if the following conditions occur due to file system corruption. (1) Condition for exfat_count_dir_entries() to loop infinitely. - The cluster chain includes a loop. - There is no UNUSED entry in the cluster chain. (2) Condition for exfat_create_upcase_table() to loop infinitely. - The cluster chain of the root directory includes a loop. - There are no UNUSED entry and up-case table entry in the cluster chain of the root directory. (3) Condition for exfat_load_bitmap() to loop infinitely. - The cluster chain of the root directory includes a loop. - There are no UNUSED entry and bitmap entry in the cluster chain of the root directory. (4) Condition for exfat_find_dir_entry() to loop infinitely. - The cluster chain includes a loop. - The unused directory entries were exhausted by some operation. (5) Condition for exfat_check_dir_empty() to loop infinitely. - The cluster chain includes a loop. - The unused directory entries were exhausted by some operation. - All files and sub-directories under the directory are deleted. This commit adds checks to break the above infinite loop. Signed-off-by: Yuezhang Mo Signed-off-by: Namjae Jeon Signed-off-by: Sasha Levin --- fs/exfat/dir.c | 12 ++++++++++++ fs/exfat/fatent.c | 10 ++++++++++ fs/exfat/namei.c | 5 +++++ fs/exfat/super.c | 32 +++++++++++++++++++++----------- 4 files changed, 48 insertions(+), 11 deletions(-) diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c index dda10bca9ac98..d8c789d768076 100644 --- a/fs/exfat/dir.c +++ b/fs/exfat/dir.c @@ -943,6 +943,7 @@ int exfat_find_dir_entry(struct super_block *sb, struct exfat_inode_info *ei, struct exfat_hint_femp candi_empty; struct exfat_sb_info *sbi = EXFAT_SB(sb); int num_entries = exfat_calc_num_entries(p_uniname); + unsigned int clu_count = 0; if (num_entries < 0) return num_entries; @@ -1100,6 +1101,10 @@ int exfat_find_dir_entry(struct super_block *sb, struct exfat_inode_info *ei, } else { if (exfat_get_next_cluster(sb, &clu.dir)) return -EIO; + + /* break if the cluster chain includes a loop */ + if (unlikely(++clu_count > EXFAT_DATA_CLUSTER_COUNT(sbi))) + goto not_found; } } @@ -1178,6 +1183,7 @@ int exfat_count_dir_entries(struct super_block *sb, struct exfat_chain *p_dir) int i, count = 0; int dentries_per_clu; unsigned int entry_type; + unsigned int clu_count = 0; struct exfat_chain clu; struct exfat_dentry *ep; struct exfat_sb_info *sbi = EXFAT_SB(sb); @@ -1210,6 +1216,12 @@ int exfat_count_dir_entries(struct super_block *sb, struct exfat_chain *p_dir) } else { if (exfat_get_next_cluster(sb, &(clu.dir))) return -EIO; + + if (unlikely(++clu_count > sbi->used_clusters)) { + exfat_fs_error(sb, "FAT or bitmap is corrupted"); + return -EIO; + } + } } diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c index e7e160d022566..bacd68bc7b8a0 100644 --- a/fs/exfat/fatent.c +++ b/fs/exfat/fatent.c @@ -470,5 +470,15 @@ int exfat_count_num_clusters(struct super_block *sb, } *ret_count = count; + + /* + * since exfat_count_used_clusters() is not called, sbi->used_clusters + * cannot be used here. + */ + if (unlikely(i == sbi->num_clusters && clu != EXFAT_EOF_CLUSTER)) { + exfat_fs_error(sb, "The cluster chain has a loop"); + return -EIO; + } + return 0; } diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c index 7f84ea80c8a6c..605c9d617d7c4 100644 --- a/fs/exfat/namei.c +++ b/fs/exfat/namei.c @@ -892,6 +892,7 @@ static int exfat_check_dir_empty(struct super_block *sb, { int i, dentries_per_clu; unsigned int type; + unsigned int clu_count = 0; struct exfat_chain clu; struct exfat_dentry *ep; struct exfat_sb_info *sbi = EXFAT_SB(sb); @@ -928,6 +929,10 @@ static int exfat_check_dir_empty(struct super_block *sb, } else { if (exfat_get_next_cluster(sb, &(clu.dir))) return -EIO; + + /* break if the cluster chain includes a loop */ + if (unlikely(++clu_count > EXFAT_DATA_CLUSTER_COUNT(sbi))) + break; } } diff --git a/fs/exfat/super.c b/fs/exfat/super.c index 52b852a4121b0..e377fbc6e847e 100644 --- a/fs/exfat/super.c +++ b/fs/exfat/super.c @@ -336,13 +336,12 @@ static void exfat_hash_init(struct super_block *sb) INIT_HLIST_HEAD(&sbi->inode_hashtable[i]); } -static int exfat_read_root(struct inode *inode) +static int exfat_read_root(struct inode *inode, struct exfat_chain *root_clu) { struct super_block *sb = inode->i_sb; struct exfat_sb_info *sbi = EXFAT_SB(sb); struct exfat_inode_info *ei = EXFAT_I(inode); - struct exfat_chain cdir; - int num_subdirs, num_clu = 0; + int num_subdirs; exfat_chain_set(&ei->dir, sbi->root_dir, 0, ALLOC_FAT_CHAIN); ei->entry = -1; @@ -355,12 +354,9 @@ static int exfat_read_root(struct inode *inode) ei->hint_stat.clu = sbi->root_dir; ei->hint_femp.eidx = EXFAT_HINT_NONE; - exfat_chain_set(&cdir, sbi->root_dir, 0, ALLOC_FAT_CHAIN); - if (exfat_count_num_clusters(sb, &cdir, &num_clu)) - return -EIO; - i_size_write(inode, num_clu << sbi->cluster_size_bits); + i_size_write(inode, EXFAT_CLU_TO_B(root_clu->size, sbi)); - num_subdirs = exfat_count_dir_entries(sb, &cdir); + num_subdirs = exfat_count_dir_entries(sb, root_clu); if (num_subdirs < 0) return -EIO; set_nlink(inode, num_subdirs + EXFAT_MIN_SUBDIR); @@ -580,7 +576,8 @@ static int exfat_verify_boot_region(struct super_block *sb) } /* mount the file system volume */ -static int __exfat_fill_super(struct super_block *sb) +static int __exfat_fill_super(struct super_block *sb, + struct exfat_chain *root_clu) { int ret; struct exfat_sb_info *sbi = EXFAT_SB(sb); @@ -597,6 +594,18 @@ static int __exfat_fill_super(struct super_block *sb) goto free_bh; } + /* + * Call exfat_count_num_cluster() before searching for up-case and + * bitmap directory entries to avoid infinite loop if they are missing + * and the cluster chain includes a loop. + */ + exfat_chain_set(root_clu, sbi->root_dir, 0, ALLOC_FAT_CHAIN); + ret = exfat_count_num_clusters(sb, root_clu, &root_clu->size); + if (ret) { + exfat_err(sb, "failed to count the number of clusters in root"); + goto free_bh; + } + ret = exfat_create_upcase_table(sb); if (ret) { exfat_err(sb, "failed to load upcase table"); @@ -631,6 +640,7 @@ static int exfat_fill_super(struct super_block *sb, struct fs_context *fc) struct exfat_sb_info *sbi = sb->s_fs_info; struct exfat_mount_options *opts = &sbi->options; struct inode *root_inode; + struct exfat_chain root_clu; int err; if (opts->allow_utime == (unsigned short)-1) @@ -649,7 +659,7 @@ static int exfat_fill_super(struct super_block *sb, struct fs_context *fc) sb->s_time_min = EXFAT_MIN_TIMESTAMP_SECS; sb->s_time_max = EXFAT_MAX_TIMESTAMP_SECS; - err = __exfat_fill_super(sb); + err = __exfat_fill_super(sb, &root_clu); if (err) { exfat_err(sb, "failed to recognize exfat type"); goto check_nls_io; @@ -684,7 +694,7 @@ static int exfat_fill_super(struct super_block *sb, struct fs_context *fc) root_inode->i_ino = EXFAT_ROOT_INO; inode_set_iversion(root_inode, 1); - err = exfat_read_root(root_inode); + err = exfat_read_root(root_inode, &root_clu); if (err) { exfat_err(sb, "failed to initialize root inode"); goto put_inode; -- 2.53.0