[PATCH review 07/13] mnt: Move the FS_USERNS_MOUNT check into sget_userns

["Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>]

Allowing a filesystem to be mounted by other than root in the initial
user namespace is a filesystem property not a mount namespace property
and as such should be checked in filesystem specific code.  Move the
FS_USERNS_MOUNT test into super.c:sget_userns().

Signed-off-by: "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
---
 fs/namespace.c | 4 ----
 fs/super.c     | 4 ++++
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 1a69aa786975..2e13f6cfe5df 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2397,10 +2397,6 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
 		return -ENODEV;
 
 	if (user_ns != &init_user_ns) {
-		if (!(type->fs_flags & FS_USERNS_MOUNT)) {
-			put_filesystem(type);
-			return -EPERM;
-		}
 		/* Only in special cases allow devices from mounts
 		 * created outside the initial user namespace.
 		 */
diff --git a/fs/super.c b/fs/super.c
index 874c7e3ebb8f..78790ada7191 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -466,6 +466,10 @@ struct super_block *sget_userns(struct file_system_type *type,
 	struct super_block *old;
 	int err;
 
+	if (!(flags & MS_KERNMOUNT) &&
+	    !(type->fs_flags & FS_USERNS_MOUNT) &&
+	    !capable(CAP_SYS_ADMIN))
+		return ERR_PTR(-EPERM);
 retry:
 	spin_lock(&sb_lock);
 	if (test) {
-- 
2.8.3