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>

diff --git a/fs/fsopen.c b/fs/fsopen.c
index c2891e933ef17e2fe326bc3eef2a11cb4c982cd3..390172772f55b78256a64bd9ed3a0fb0e459d76e 100644 (file)
--- a/fs/fsopen.c
+++ b/fs/fsopen.c
@@ -230,6 +230,8 @@ static int vfs_fsconfig_locked(struct fs_context *fc, int cmd,
        case FSCONFIG_CMD_CREATE:
                if (fc->phase != FS_CONTEXT_CREATE_PARAMS)
                        return -EBUSY;
+               if (!mount_capable(fc))
+                       return -EPERM;
                fc->phase = FS_CONTEXT_CREATING;
                ret = vfs_get_tree(fc);
                if (ret)

diff --git a/fs/namespace.c b/fs/namespace.c
index ffb13f0562b0702df6c22724b0557c6fb789d732..1141641dff9605b6f729080a31e1f1d82f337fea 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2786,6 +2786,8 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
                err = vfs_parse_fs_string(fc, "source", name, strlen(name));
        if (!err)
                err = parse_monolithic_mount_data(fc, data);
+       if (!err && !mount_capable(fc))
+               err = -EPERM;
        if (!err)
                err = vfs_get_tree(fc);
        if (!err)

diff --git a/fs/super.c b/fs/super.c
index 2c38541cd89f2f569df5b1bc34033a1e5dfbf7e9..72b4a5afcfd6da3cbd7ba9cdca70f11d3df92fd9 100644 (file)
--- 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.
         */