security: remove security_sb_post_mountroot hook

The security_sb_post_mountroot() hook is long-since obsolete, and is
fundamentally broken: it is never invoked if someone uses initramfs.
This is particularly damaging, because the existence of this hook has
been used as motivation for not using initramfs.

Stephen Smalley confirmed on 2007-07-19 that this hook was originally
used by SELinux but can now be safely removed:

     http://marc.info/?l=linux-kernel&m=118485683612916&w=2

Cc: Stephen Smalley <[email protected]>
Cc: James Morris <[email protected]>
Cc: Eric Paris <[email protected]>
Cc: Chris Wright <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
Signed-off-by: James Morris <[email protected]>

Author: H. Peter Anvin

include/linux/security.h

@@ -249,9 +249,6 @@ struct request_sock;
  *	@mnt contains the mounted file system.
  *	@flags contains the new filesystem flags.
  *	@data contains the filesystem-specific data.
- * @sb_post_mountroot:
- *	Update the security module's state when the root filesystem is mounted.
- *	This hook is only called if the mount was successful.
  * @sb_post_addmount:
  *	Update the security module's state when a filesystem is mounted.
  *	This hook is called any time a mount is successfully grafetd to
@@ -1257,7 +1254,6 @@ struct security_operations {
 	void (*sb_umount_busy) (struct vfsmount * mnt);
 	void (*sb_post_remount) (struct vfsmount * mnt,
 				 unsigned long flags, void *data);
-	void (*sb_post_mountroot) (void);
 	void (*sb_post_addmount) (struct vfsmount * mnt,
 				  struct nameidata * mountpoint_nd);
 	int (*sb_pivotroot) (struct nameidata * old_nd,
@@ -1524,7 +1520,6 @@ int security_sb_umount(struct vfsmount *mnt, int flags);
 void security_sb_umount_close(struct vfsmount *mnt);
 void security_sb_umount_busy(struct vfsmount *mnt);
 void security_sb_post_remount(struct vfsmount *mnt, unsigned long flags, void *data);
-void security_sb_post_mountroot(void);
 void security_sb_post_addmount(struct vfsmount *mnt, struct nameidata *mountpoint_nd);
 int security_sb_pivotroot(struct nameidata *old_nd, struct nameidata *new_nd);
 void security_sb_post_pivotroot(struct nameidata *old_nd, struct nameidata *new_nd);
@@ -1813,9 +1808,6 @@ static inline void security_sb_post_remount (struct vfsmount *mnt,
 					     unsigned long flags, void *data)
 { }
 
-static inline void security_sb_post_mountroot (void)
-{ }
-
 static inline void security_sb_post_addmount (struct vfsmount *mnt,
 					      struct nameidata *mountpoint_nd)
 { }

init/do_mounts.c

@@ -470,6 +470,5 @@ void __init prepare_namespace(void)
 out:
 	sys_mount(".", "/", NULL, MS_MOVE, NULL);
 	sys_chroot(".");
-	security_sb_post_mountroot();
 }
 

security/dummy.c

@@ -225,11 +225,6 @@ static void dummy_sb_post_remount (struct vfsmount *mnt, unsigned long flags,
 }
 
 
-static void dummy_sb_post_mountroot (void)
-{
-	return;
-}
-
 static void dummy_sb_post_addmount (struct vfsmount *mnt, struct nameidata *nd)
 {
 	return;
@@ -1017,7 +1012,6 @@ void security_fixup_ops (struct security_operations *ops)
 	set_to_dummy_if_null(ops, sb_umount_close);
 	set_to_dummy_if_null(ops, sb_umount_busy);
 	set_to_dummy_if_null(ops, sb_post_remount);
-	set_to_dummy_if_null(ops, sb_post_mountroot);
 	set_to_dummy_if_null(ops, sb_post_addmount);
 	set_to_dummy_if_null(ops, sb_pivotroot);
 	set_to_dummy_if_null(ops, sb_post_pivotroot);

security/security.c

@@ -288,11 +288,6 @@ void security_sb_post_remount(struct vfsmount *mnt, unsigned long flags, void *d
 	security_ops->sb_post_remount(mnt, flags, data);
 }
 
-void security_sb_post_mountroot(void)
-{
-	security_ops->sb_post_mountroot();
-}
-
 void security_sb_post_addmount(struct vfsmount *mnt, struct nameidata *mountpoint_nd)
 {
 	security_ops->sb_post_addmount(mnt, mountpoint_nd);