ext2: Avoid reading renamed directory if parent does not change

The VFS will not be locking moved directory if its parent does not
change. Change ext2 rename code to avoid reading renamed directory if
its parent does not change. Although it is currently harmless it is a
bad practice to read directory contents without inode->i_rwsem.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
index 65f702b1da5b0f56b80d6d429a8e557d33ed2781..8346ab9534c17ab62730bfebd03b23f0af9dd141 100644 (file)
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -325,6 +325,7 @@ static int ext2_rename (struct mnt_idmap * idmap,
        struct ext2_dir_entry_2 * dir_de = NULL;
        struct folio * old_folio;
        struct ext2_dir_entry_2 * old_de;
+       bool old_is_dir = S_ISDIR(old_inode->i_mode);
        int err;
 
        if (flags & ~RENAME_NOREPLACE)
@@ -342,7 +343,7 @@ static int ext2_rename (struct mnt_idmap * idmap,
        if (IS_ERR(old_de))
                return PTR_ERR(old_de);
 
-       if (S_ISDIR(old_inode->i_mode)) {
+       if (old_is_dir && old_dir != new_dir) {
                err = -EIO;
                dir_de = ext2_dotdot(old_inode, &dir_folio);
                if (!dir_de)
@@ -354,7 +355,7 @@ static int ext2_rename (struct mnt_idmap * idmap,
                struct ext2_dir_entry_2 *new_de;
 
                err = -ENOTEMPTY;
-               if (dir_de && !ext2_empty_dir (new_inode))
+               if (old_is_dir && !ext2_empty_dir(new_inode))
                        goto out_dir;
 
                new_de = ext2_find_entry(new_dir, &new_dentry->d_name,
@@ -368,14 +369,14 @@ static int ext2_rename (struct mnt_idmap * idmap,
                if (err)
                        goto out_dir;
                inode_set_ctime_current(new_inode);
-               if (dir_de)
+               if (old_is_dir)
                        drop_nlink(new_inode);
                inode_dec_link_count(new_inode);
        } else {
                err = ext2_add_link(new_dentry, old_inode);
                if (err)
                        goto out_dir;
-               if (dir_de)
+               if (old_is_dir)
                        inode_inc_link_count(new_dir);
        }
 
@@ -387,7 +388,7 @@ static int ext2_rename (struct mnt_idmap * idmap,
        mark_inode_dirty(old_inode);
 
        err = ext2_delete_entry(old_de, old_folio);
-       if (!err && dir_de) {
+       if (!err && old_is_dir) {
                if (old_dir != new_dir)
                        err = ext2_set_link(old_inode, dir_de, dir_folio,
                                            new_dir, false);