*statfs exposure of file system IDs to non-root users

[Terry Lambert]

Ian Dowse wrote:
> In changing umount(8) to use statfs(2), I just noticed that the
> various *statfs calls hide the filesystem IDs from non-root users:
> 
>         if (suser(td)) {
>                 bcopy(sp, &sb, sizeof(sb));
>                 sb.f_fsid.val[0] = sb.f_fsid.val[1] = 0;
>                 sp = &sb;
>         }
> 
> This was added in vfs_syscalls.c revision 1.61 (March 1997) and
> came from OpenBSD. I guess the reason was to hide information that
> gets used in NFS filehandles, but it doesn't do us any good now as
> you can get the real IDs from getfsstat() as a normal user. Being
> able to get and compare file system IDs is useful for umount, and
> umount can be used by non-root users when vfs.usermount is set.
> 
> Is there a good reason not to delete this fsid hiding?

The real question is "Why do you need this information?".

If you can answer that, we can probably tell you a different
approach to solving your problem.

-- Terry