On Sun, 2014-11-02 at 02:34 +0100, Christian Hofstaedtler wrote: > * Ben Hutchings <[email protected]> [141101 14:02]: > > On Sat, 2014-11-01 at 13:22 +0100, Christian Hofstaedtler wrote: > > > * Ben Hutchings <[email protected]> [141101 06:26]: > > > > On Sat, 2014-11-01 at 04:44 +0100, Christian Hofstaedtler wrote: > > > > > I've tried to debug this a bit more tonight, and after a good 4 > > > > > hours there are two things I can report: > > > > > > > > > > 1. with the default ruleset, udev leaks an ethtool socket to > > > > > net.agent (and by extension to ifup, dhclient, ...) > > > > > > > > This is a bug but probably harmless. SIOCETHTOOL doesn't depend on any > > > > socket state so it is normally used with an unconnected socket of an > > > > arbitrary address family. > > > > > > While it may be harmless from a security POV, the leaked FD causes > > > the udev worker to hold on to the forked-away net.agent process. > > > > How is that? > > You're obviously correct; the extra FDs are red herrings. > > dash "backs up" any FDs it redirects, so it can restore them > later on. bash just closes them outright in this situation (forked > subshell + parent exits), causing udev's spawn_read to immediately, > thereby marking the udev event as finished.
That makes *much* more sense.
[...]
> I'd suggest the following patch, as a stop gap for sysvinit users:
>
> Index: systemd-215/debian/extra/net.agent
> ===================================================================
> --- systemd-215.orig/debian/extra/net.agent 2014-09-27 17:50:52.000000000
> +0200
> +++ systemd-215/debian/extra/net.agent 2014-11-02 02:33:40.970469131 +0100
> @@ -1,4 +1,4 @@
> -#!/bin/sh -e
> +#!/bin/bash -e
> #
> # run /sbin/{ifup,ifdown} with the --allow=hotplug option.
> #
> @@ -100,9 +100,12 @@ esac
>
> }
>
> -# When udev_log="debug" stdout and stderr are pipes connected to udevd.
> +# When udev_log="info" (default) or "debug", stdout and stderr are
> +# pipes connected to udevd.
> # They need to be closed or udevd will wait for this process which will
> # deadlock with udevsettle until the timeout.
> +# Note that this trick does not work under dash, which "backs up" any
> +# redirected FDs to FD 10 and higher.
> do_everything > /dev/null 2> /dev/null &
This seems to work under both bash and dash:
exec > /dev/null 2> /dev/null
do_everything &
Ben.
> exit 0
>
--
Ben Hutchings
A free society is one where it is safe to be unpopular. - Adlai Stevenson
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