On 1/31/2014 2:30 PM, Alexander Leidinger wrote: > On Fri, 31 Jan 2014 12:34:48 +0000 (GMT) > Robert Watson <rwat...@freebsd.org> wrote: >> On Wed, 29 Jan 2014, Alexander Leidinger wrote: >>>> It does. I included a warning in jail.8 that this will pretty >>>> much undo jail security. There are still reasons some may want to >>>> do this, but it's definitely not for everyone or even most people. >>> >>> It only "unjails" (= basically the same security level as the >>> jail-host with the added benefit of the flexibility of a jail like >>> easy moving from one system to another) the jail which has this >>> flag set. All other jails without the flag can not "escape" to the >>> host. >>> >>> I also have to add that just setting this flag does not give access >>> to the host, you also have to configure a non-default devfs rule >>> for this jail (to have the devices appear in the jail). >> >> This is not correct: devices do not need to be delegated in devfs for >> PRIV_IO to allow bypass of the Jail security model, due to sysarch() >> and the Linux-emulated equivalent, which turn out direct I/O access >> from a user process without use of a device node. > > Ok, then it is just the non-default flag, not the additional devfs part. > > I agree with your other post that we are better of to document better > what it means if an admin allows kmem access for a specific jail.
I second the documentation route. Yes, it's true that this option makes a totally insecure jail - at least one lacking the expected jail security additions. But I think that while security is one of the primary purposes of jails, it's not the only purpose. It should be possible to have a trusted "master jail" that still takes advantage of the encapsulation while allowing otherwise unsupported features such as a desktop. The distinction of whether certain devices are required to break out of a jail with allow.kmem is something of a red herring - the fact is that anyone who wants this level of access is going to have the devices in place anyway. I suppose "obviate" wasn't the best word for the situation. Maybe something that starts with "WARNING: ..." is in order. I'd like to re-submit the patch with only the documentation changed (unless someone knows of something that would accomplish the same goals with different code). But I'll run it by secteam@ first, and abide by the consensus there. - Jamie _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
