5.4-stable review patch. If anyone has any objections, please let me know.
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From: Baokun Li libaokun1@huawei.com
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 libaokun1@huawei.com Reviewed-by: Jan Kara jack@suse.cz Link: https://patch.msgid.link/20240702132349.2600605-3-libaokun@huaweicloud.com Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ext4/namei.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-)
--- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -135,10 +135,11 @@ static struct buffer_head *__ext4_read_d
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) @@ -2945,10 +2946,7 @@ bool ext4_empty_dir(struct inode *inode) EXT4_ERROR_INODE(inode, "invalid size"); return true; } - /* 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 true;
@@ -3542,10 +3540,7 @@ static struct buffer_head *ext4_get_firs 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;