lsm: add new securityfs delete function

When deleting a directory in the security file system, the existing
securityfs_remove requires the directory to be empty, otherwise
it will do nothing. This leads to a potential risk that the security
file system might be in an unclean state when the intended deletion
did not happen.

This commit introduces a new function securityfs_recursive_remove
to recursively delete a directory without leaving an unclean state.

Co-developed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
[PM: subject line tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>

include/linux/security.h

@@ -2090,6 +2090,7 @@ struct dentry *securityfs_create_symlink(const char *name,
 					 const char *target,
 					 const struct inode_operations *iops);
 extern void securityfs_remove(struct dentry *dentry);
+extern void securityfs_recursive_remove(struct dentry *dentry);
 
 #else /* CONFIG_SECURITYFS */