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Date:   Fri, 15 Mar 2019 16:54:40 -0700
From:   Jakub Kicinski <jakub.kicinski@netronome.com>
To:     Trond Myklebust <trond.myklebust@hammerspace.com>
Cc:     linux-nfs@vger.kernel.org,
        Anna Schumaker <anna.schumaker@netapp.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Kees Cook <keescook@chromium.org>
Subject: Re: mount.nfs: Protocol error after upgrade to linux/master
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In-Reply-To: <20190315120105.5541ad46@cakuba.netronome.com>
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        <20190315120105.5541ad46@cakuba.netronome.com>
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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@davemloft.net>
> > Date:   Mon Mar 11 16:22:49 2019 -0700
> > 
> > to
> > 
> > commit 3b319ee220a8795406852a897299dbdfc1b09911
> > Merge: 9352ca585b2a b6e88119f1ed
> > Author: Linus Torvalds <torvalds@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...