vfs: add cross-rename

If flags contain RENAME_EXCHANGE then exchange source and destination files.
There's no restriction on the type of the files; e.g. a directory can be
exchanged with a symlink.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/security/security.c b/security/security.c
index 284fbc99aa9d..8b774f362a3d 100644
--- a/security/security.c
+++ b/security/security.c
@@ -439,6 +439,14 @@ int security_path_rename(struct path *old_dir, struct dentry *old_dentry,
         if (unlikely(IS_PRIVATE(old_dentry->d_inode) ||
                      (new_dentry->d_inode && IS_PRIVATE(new_dentry->d_inode))))
                 return 0;
+
+        if (flags & RENAME_EXCHANGE) {
+                int err = security_ops->path_rename(new_dir, new_dentry,
+                                                    old_dir, old_dentry);
+                if (err)
+                        return err;
+        }
+
         return security_ops->path_rename(old_dir, old_dentry, new_dir,
                                          new_dentry);
 }
@@ -531,6 +539,14 @@ int security_inode_rename(struct inode *old_dir, struct dentry *old_dentry,
         if (unlikely(IS_PRIVATE(old_dentry->d_inode) ||
             (new_dentry->d_inode && IS_PRIVATE(new_dentry->d_inode))))
                 return 0;
+
+        if (flags & RENAME_EXCHANGE) {
+                int err = security_ops->inode_rename(new_dir, new_dentry,
+                                                     old_dir, old_dentry);
+                if (err)
+                        return err;
+        }
+
         return security_ops->inode_rename(old_dir, old_dentry,
                                            new_dir, new_dentry);
 }