mount.nfs: Protocol error after upgrade to linux/master

[Kees Cook]

On Fri, Mar 15, 2019 at 4:54 PM Jakub Kicinski
<jakub.kicinski at netronome.com> wrote:
>
> On Fri, 15 Mar 2019 12:01:05 -0700, Jakub Kicinski wrote:
> > On Fri, 15 Mar 2019 11:05:55 -0700, Jakub Kicinski wrote:
> > > Hi,
> > >
> > > I just upgraded from:
> > >
> > > commit a3b1933d34d5bb26d7503752e3528315a9e28339 (net)
> > > Merge: c6873d18cb4a 24319258660a
> > > Author: David S. Miller <davem at davemloft.net>
> > > Date:   Mon Mar 11 16:22:49 2019 -0700
> > >
> > > to
> > >
> > > commit 3b319ee220a8795406852a897299dbdfc1b09911
> > > Merge: 9352ca585b2a b6e88119f1ed
> > > Author: Linus Torvalds <torvalds at linux-foundation.org>
> > > Date:   Thu Mar 14 10:48:14 2019 -0700
> > >
> > > and I'm seeing:
> > >
> > > # mount /home/
> > > mount.nfs: Protocol error
> > >
> > > No errors in dmesg, please let me know if it's a known problem or what
> > > other info could be of use.
> >
> > Hm.. I tried to bisect but reverting to that commit doesn't help.
> >
> > Looks like the server responds with:
> >
> >   ICMP parameter problem - octet 22, length 80
> >
> > pointing at some IP options (type 134)...
>
> Okay, figured it out, it's the commit 13e735c0e953 ("LSM: Introduce
> CONFIG_LSM") and all the related changes in security/
>
> I did olddefconfig and it changed my security module from apparmor to
> smack silently.  smack must be slapping those IP options on by default.
>
> Pretty awful user experience, and a non-zero chance that users who
> upgrade their kernels will miss this and end up with the wrong security
> module...

I wonder if we can add some kind of logic to Kconfig to retain the old
CONFIG_DEFAULT_SECURITY and include it as the first legacy-major LSM
listed in CONFIG_LSM?

Like, but the old selector back in, but mark is as "soon to be
entirely replaced with CONFIG_LSM" and then make CONFIG_LSM's default
be "yama,loadpin,safesetid,integrity,$(CONFIG_DEFAULT_SECURITY),selinux,smack,tomoyo,apparmor"
? Duplicates are ignored...

-- 
Kees Cook