[PATCH 1/2] fs: add loopback/bind mount specific security hook

[kernel test robot]

Hi Shervin,

kernel test robot noticed the following build errors:

[auto build test ERROR on fc033cf25e612e840e545f8d5ad2edd6ba613ed5]

url:    https://github.com/intel-lab-lkp/linux/commits/Shervin-Oloumi/landlock-add-support-for-private-bind-mount/20241231-094806
base:   fc033cf25e612e840e545f8d5ad2edd6ba613ed5
patch link:    https://lore.kernel.org/r/20241231014632.589049-1-enlightened%40chromium.org
patch subject: [PATCH 1/2] fs: add loopback/bind mount specific security hook
config: sparc-randconfig-002-20241231 (https://download.01.org/0day-ci/archive/20241231/202412311303.Cb16SNL3-lkp@intel.com/config)
compiler: sparc-linux-gcc (GCC) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241231/202412311303.Cb16SNL3-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp at intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202412311303.Cb16SNL3-lkp@intel.com/

All errors (new ones prefixed by >>):

   fs/namespace.c: In function 'do_loopback':
>> fs/namespace.c:2768:15: error: implicit declaration of function 'security_sb_bindmount'; did you mean 'security_sb_umount'? [-Wimplicit-function-declaration]
    2768 |         err = security_sb_bindmount(&old_path, path);
         |               ^~~~~~~~~~~~~~~~~~~~~
         |               security_sb_umount


vim +2768 fs/namespace.c

  2751	
  2752	/*
  2753	 * do loopback mount.
  2754	 */
  2755	static int do_loopback(struct path *path, const char *old_name,
  2756					int recurse)
  2757	{
  2758		struct path old_path;
  2759		struct mount *mnt = NULL, *parent;
  2760		struct mountpoint *mp;
  2761		int err;
  2762		if (!old_name || !*old_name)
  2763			return -EINVAL;
  2764		err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
  2765		if (err)
  2766			return err;
  2767	
> 2768		err = security_sb_bindmount(&old_path, path);
  2769		if (err)
  2770			goto out;
  2771	
  2772		err = -EINVAL;
  2773		if (mnt_ns_loop(old_path.dentry))
  2774			goto out;
  2775	
  2776		mp = lock_mount(path);
  2777		if (IS_ERR(mp)) {
  2778			err = PTR_ERR(mp);
  2779			goto out;
  2780		}
  2781	
  2782		parent = real_mount(path->mnt);
  2783		if (!check_mnt(parent))
  2784			goto out2;
  2785	
  2786		mnt = __do_loopback(&old_path, recurse);
  2787		if (IS_ERR(mnt)) {
  2788			err = PTR_ERR(mnt);
  2789			goto out2;
  2790		}
  2791	
  2792		err = graft_tree(mnt, parent, mp);
  2793		if (err) {
  2794			lock_mount_hash();
  2795			umount_tree(mnt, UMOUNT_SYNC);
  2796			unlock_mount_hash();
  2797		}
  2798	out2:
  2799		unlock_mount(mp);
  2800	out:
  2801		path_put(&old_path);
  2802		return err;
  2803	}
  2804	

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