From b609753cbbd38f8c0affd4956c0af178348523ac Mon Sep 17 00:00:00 2001 From: Baokun Li Date: Tue, 2 Jul 2024 21:23:49 +0800 Subject: [PATCH] ext4: make sure the first directory block is not a hole commit f9ca51596bbfd0f9c386dd1c613c394c78d9e5e6 upstream. The syzbot constructs a directory that has no dirblock but is non-inline, i.e. the first directory block is a hole. And no errors are reported when creating files in this directory in the following flow. ext4_mknod ... ext4_add_entry // Read block 0 ext4_read_dirblock(dir, block, DIRENT) bh = ext4_bread(NULL, inode, block, 0) if (!bh && (type == INDEX || type == DIRENT_HTREE)) // The first directory block is a hole // But type == DIRENT, so no error is reported. After that, we get a directory block without '.' and '..' but with a valid dentry. This may cause some code that relies on dot or dotdot (such as make_indexed_dir()) to crash. Therefore when ext4_read_dirblock() finds that the first directory block is a hole report that the filesystem is corrupted and return an error to avoid loading corrupted data from disk causing something bad. Reported-by: syzbot+ae688d469e36fb5138d0@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=ae688d469e36fb5138d0 Fixes: 4e19d6b65fb4 ("ext4: allow directory holes") Cc: stable@kernel.org Signed-off-by: Baokun Li Reviewed-by: Jan Kara Link: https://patch.msgid.link/20240702132349.2600605-3-libaokun@huaweicloud.com Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/ext4/namei.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-) diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 072bf0a68729..173f46fa1068 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -151,10 +151,11 @@ static struct buffer_head *__ext4_read_dirblock(struct inode *inode, return bh; } - if (!bh && (type == INDEX || type == DIRENT_HTREE)) { + /* The first directory block must not be a hole. */ + if (!bh && (type == INDEX || type == DIRENT_HTREE || block == 0)) { ext4_error_inode(inode, func, line, block, - "Directory hole found for htree %s block", - (type == INDEX) ? "index" : "leaf"); + "Directory hole found for htree %s block %u", + (type == INDEX) ? "index" : "leaf", block); return ERR_PTR(-EFSCORRUPTED); } if (!bh) @@ -3133,10 +3134,7 @@ bool ext4_empty_dir(struct inode *inode) EXT4_ERROR_INODE(inode, "invalid size"); return false; } - /* The first directory block must not be a hole, - * so treat it as DIRENT_HTREE - */ - bh = ext4_read_dirblock(inode, 0, DIRENT_HTREE); + bh = ext4_read_dirblock(inode, 0, EITHER); if (IS_ERR(bh)) return false; @@ -3580,10 +3578,7 @@ static struct buffer_head *ext4_get_first_dir_block(handle_t *handle, struct ext4_dir_entry_2 *de; unsigned int offset; - /* The first directory block must not be a hole, so - * treat it as DIRENT_HTREE - */ - bh = ext4_read_dirblock(inode, 0, DIRENT_HTREE); + bh = ext4_read_dirblock(inode, 0, EITHER); if (IS_ERR(bh)) { *retval = PTR_ERR(bh); return NULL;