[SRU][Cosmic][Bionic][PATCH 0/6] Fixes for LP1797367

[Frank Heimes]

BugLink: http://bugs.launchpad.net/bugs/1797367

== SRU Justification ==

While running a series of stress tests for network on a bond device on
Ubuntu 18.04.1 with kernel 4.15.0-36.39,
kernel panic is observed (btw. also on non-bond devices).
This looks like a race between disabling a qeth device and accessing debugfs.
This is critical and leads repeatedly to a crash (sooner or later).

== Fix ==

e19e5be8b4ca ("s390/qeth: sanitize strings in debug messages")

pre-reqs:
750b162 ("s390/qeth: reduce hard-coded access to ccw channels")
d857e11 ("s390/qeth: remove outdated portname debug msg")
9d0a58f ("s390/qeth: avoid using is_multicast_ether_addr_64bits on (u8 *)[6]")
8174aa8 ("s390/qeth: consolidate qeth MAC address helpers")
4641b02 ("s390/qeth: don't keep track of MAC address's cast type")

== Regression Potential ==

Low, because:
- limited to s390x
- and furthermore limited to qeth driver
- patches a problem identified during testing
- fix was tested by IBM before submitted

== Test Case ==

run:
   #!/bin/bash
   var=0
   while :
   do
        var=$((var + 1))
        echo "DBG count is $var"
        mkdir /tmp/DBGINFO
        dbginfo.sh -d /tmp/DBGINFO
        rm -rf /tmp/DBGINFO*
        echo "chzdev now is $var"
        chzdev -e <qeth device>
        chzdev -d <qeth device>
   done
and in avg. in less than 20 cycles a crash happens (usually < 10).