move mount_capable() further out

Call graph of vfs_get_tree():
	vfs_fsconfig_locked()	# neither kernmount, nor submount
	do_new_mount()		# neither kernmount, nor submount
	fc_mount()
		afs_mntpt_do_automount()	# submount
		mount_one_hugetlbfs()		# kernmount
		pid_ns_prepare_proc()		# kernmount
		mq_create_mount()		# kernmount
		vfs_kern_mount()
			simple_pin_fs()		# kernmount
			vfs_submount()		# submount
			kern_mount()		# kernmount
			init_mount_tree()
			btrfs_mount()
			nfs_do_root_mount()

	The first two need the check (unconditionally).
init_mount_tree() is setting rootfs up; any capability
checks make zero sense for that one.  And btrfs_mount()/
nfs_do_root_mount() have the checks already done in their
callers.

	IOW, we can shift mount_capable() handling into
the two callers - one in the normal case of mount(2),
another - in fsconfig(2) handling of FSCONFIG_CMD_CREATE.
I.e. the syscalls that set a new filesystem up.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 0 insertions, 6 deletions

diff --git a/fs/super.c b/fs/super.c
index 2c38541cd89f..72b4a5afcfd6 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1415,12 +1415,6 @@ int vfs_get_tree(struct fs_context *fc)
 	if (fc->root)
 		return -EBUSY;
 
-	if (!(fc->sb_flags & SB_KERNMOUNT) &&
-	    fc->purpose != FS_CONTEXT_FOR_SUBMOUNT) {
-		if (!mount_capable(fc))
-			return -EPERM;
-	}
-
 	/* Get the mountable root in fc->root, with a ref on the root and a ref
 	 * on the superblock.
 	 */