Date: Wed, 17 Sep 2014 13:45:25 -0700 From: Peter Wemm <peter@wemm.org> To: freebsd-current@freebsd.org Cc: Patrick Kelsey <kelsey@ieee.org>, George Neville-Neil <gnn@freebsd.org>, Mateusz Guzik <mjguzik@gmail.com> Subject: Re: _ftello() modification requires additional capsicum rights, breaking tcpdump and dhclient Message-ID: <52259934.QGKubh7NGh@overcee.wemm.org> In-Reply-To: <20140916104236.GA21560@dft-labs.eu> References: <CAD44qMWgWn_OZ1i0Jy2WTLY=YAai%2B6-_Bq24QN-AjD9iYJ2JOA@mail.gmail.com> <4252906.DAHIEnKpIF@overcee.wemm.org> <20140916104236.GA21560@dft-labs.eu>
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[-- Attachment #1 --] On Tuesday, September 16, 2014 12:42:36 PM Mateusz Guzik wrote: > On Fri, Sep 12, 2014 at 09:29:56PM -0700, Peter Wemm wrote: > > On Thursday, September 11, 2014 12:38:02 PM Patrick Kelsey wrote: > > > On Wed, Sep 10, 2014 at 3:00 AM, Andrey Chernov <ache@freebsd.org> wrote: > > > > On 09.09.2014 21:53, Patrick Kelsey wrote: > > > > > I don't think it is worth the trouble, as given the larger pattern > > > > > of > > > > > libc routines requiring multiple capsicum rights, it seems one will > > > > > in > > > > > general have to have libc implementation knowledge when using it in > > > > > concert with capsicum. For example, consider the limitfd() routine > > > > > in > > > > > kdump.c, which provides rights for the TIOCGETA ioctl to be used on > > > > > stdout so the eventual call to isatty() via printf() will work as > > > > > > > > intended. > > > > > > > > > I think the above kdump example is a good one for the subtle issues > > > > > that > > > > > can arise when using capsicum with libc. That call to isatty() is > > > > > via a > > > > > widely-used internal libc routine __smakebuf(). __smakebuf() also > > > > > calls > > > > > __swhatbuf(), which in turn calls _fstat(), all to make sure that > > > > > output > > > > > to a tty is line buffered by default. It would appear that programs > > > > > that restrict rights on stdout without allowing CAP_IOCTL and > > > > > CAP_FSTAT > > > > > could be disabling the normally default line buffering when stdout > > > > > is a > > > > > tty. kdump goes the distance, but dhclient does not (restricting > > > > > stdout > > > > > to CAP_WRITE only). > > > > > > > > > > In any event, the patch attached to my first message is seeming like > > > > > the > > > > > way to go. > > > > > > > > Well, then commit it (if capsicum team agrees). > > > > > > Will do - thanks for the feedback. > > > > > > -Patrick > > > > Is there any possibility that this is related to the problem we've > > recently > > hit in the freebsd.org cluster with this month's refresh? > > > > After running for a while: > > Sep 10 02:39:44 ns2 unbound: [65258:0] notice: init module 0: validator > > Sep 10 02:39:44 ns2 unbound: [65258:0] notice: init module 1: iterator > > Sep 10 11:44:29 ns2 unbound: [65258:3] fatal error: event_dispatch > > returned > > error -1, errno is Capabilities insufficient > > > > Sep 10 16:21:16 ns2 unbound: [28212:0] warning: did not exit gracefully > > last time (65258) > > Sep 10 16:21:16 ns2 unbound: [28213:0] notice: init module 0: validator > > Sep 10 16:21:16 ns2 unbound: [28213:0] notice: init module 1: iterator > > Sep 11 10:23:49 ns2 unbound: [28213:5] fatal error: event_dispatch > > returned > > error -1, errno is Capabilities insufficient > > > > Sep 11 13:48:46 ns2 unbound: [79419:0] warning: did not exit gracefully > > last time (28213) > > Sep 11 13:48:46 ns2 unbound: [79420:0] notice: init module 0: validator > > Sep 11 13:48:46 ns2 unbound: [79420:0] notice: init module 1: iterator > > Sep 11 18:42:56 ns2 unbound: [79420:6] fatal error: event_dispatch > > returned > > error -1, errno is Capabilities insufficient > > > > I believe this jail was started from the boot process. If I restart the > > jail by hand from a ssh session the problem goes away. > > > > This is unbound from ports and I don't have any more details than this. > > This is new this month. > > Is this thingy multithreaded? > > Currently there is a race in the kernel where fd is visible before > relevant capabilities are installed. This can result in an error like > this one for weird processes. > > I got a patch for this: > http://lists.freebsd.org/pipermail/freebsd-arch/2014-August/015788.html > > but it got stalled on 'memory barrier' discussion. I'll try to ping > people to move it forward. > > IIRC there was a report of unbound failing this way, apparently fixed > with aforementioned patch. Yes, unbound is multi-threaded and your comment is the first potential explanation that makes sense so far. -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV UTF-8: for when a ' or ... just won\342\200\231t do\342\200\246 [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAABAgAGBQJUGfLmAAoJEDXWlwnsgJ4ENUIIAML+6cjn5sDZS/6pgu/Jfo/J c9TRcTPuBhOsG/XhsF2IklOt8NmwUYIMHm6NhzQEjTbdvzaAGlBB4EON+Hw+q0Wt FnhXArUIPhDKOhWIiLKW9Z/lC+qaJFzH1sbKs41demCeaNdtwTiIXZjkLMfeXn10 3UwHldzeWTRrt+P9oy7YIJl0sMUdwPdIgrkpysuf+e3X3YHeZEhZYb7UBHE9O0YT vAxvv+m5i5Zlz5S22JRd+q1hZYvfuHfFK6DNtHldKhtCgqdbY78AnOiEw83ZTZLa uKMqTdE9Zqliipkci8c3Rg/YjmsC6lIlmjMeJNI296R4myhddcja7nb3Q7aQWW0= =Q1vR -----END PGP SIGNATURE-----help
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