Jail nullfs mount information visibility [redirected from secteam@]

[Sergey Zakharchenko]

Hello,

I doubt this is an issue at all, but how some of the information
hiding in jails work seemed a bit illogical. FreeBSD seems to be
trying to hide nullfs mounts inside jails from the jailed proceses,
but it isn't very good or consistent at it. For example:

(inside the jail, which has a nullfs mount /path/outside/of/jail ->
/path/inside/jail/to/nullfs/mount):

# df
Filesystem                            512-blocks    Used    Avail
Capacity  Mounted on
whatever/is/jails/root/dev   ...  ... ...     ...%    /

OK, I can understand this (no nullfs mounts show up), but I don't get
the following:

# df  /path/inside/jail/to/nullfs/mount/and/deeper
Filesystem                            512-blocks    Used    Avail
Capacity  Mounted on
/path/outside/of/jail   ...  ... ...     ...%    [restricted]

Why would you hide the target of the mount point (which I supposedly
know, since I need it to issue the df command) , but expose the source
(/path/outside/of/jail)? Shouldn't it be the other way around?

# uname -a
FreeBSD e40a1050f614 10.2-RELEASE FreeBSD 10.2-RELEASE #0 r286666: Wed
Aug 12 15:26:37 UTC 2015
root at releng1.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC  amd64

Best regards,

-- 
DoubleF