Date: Fri, 31 Jan 2014 18:28:27 -0700 From: James Gritton <jamie@freebsd.org> To: Alexander Leidinger <Alexander@Leidinger.net>, Robert Watson <rwatson@FreeBSD.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, Gleb Smirnoff <glebius@FreeBSD.org>, src-committers@freebsd.org Subject: Re: svn commit: r261266 - in head: sys/dev/drm sys/kern sys/sys usr.sbin/jail Message-ID: <52EC4DBB.50804@freebsd.org> In-Reply-To: <20140131223011.0000163b@unknown> References: <201401291341.s0TDfDcB068211@svn.freebsd.org> <20140129134344.GW66160@FreeBSD.org> <52E906CD.9050202@freebsd.org> <20140129222210.0000711f@unknown> <alpine.BSF.2.00.1401311231490.36707@fledge.watson.org> <20140131223011.0000163b@unknown>
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On 1/31/2014 2:30 PM, Alexander Leidinger wrote: > On Fri, 31 Jan 2014 12:34:48 +0000 (GMT) > Robert Watson <rwatson@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
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