NFS server root_squash

[rini17]

I wanted temporarily to access read-only whole filesystem, so I exported / with (ro,no_root_squash) on grsec-enabled system. But it behaved as if root_squash was in effect, i.e. I got permission denied errors. There are no ACLs, no PaX stuff on server, just grsec-patched kernel 2.4.27.

When I exported root on another machine without grsec, I could access everything.

Is it really grsec feature? I failed to find it documented anywhere.