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 c2891e9..3901727 100644
--- 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)