linux-kernel - Re: [BREAKAGE] Since 4.18, kernel sets SB_I_NODEV implicitly on userns mounts, breaking systemd-nspawn

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Date:   Sat, 22 Dec 2018 23:12:33 -0500
From:   Ellie Reeves <ellierevves@...il.com>
To:     Gabriel C <nix.or.die@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     christian.brauner@...onical.com,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Seth Forshee <seth.forshee@...onical.com>
Subject: Re: [BREAKAGE] Since 4.18, kernel sets SB_I_NODEV implicitly on
 userns mounts, breaking systemd-nspawn

Hi,
I would like to thank you all for reacting to this issue so quickly, and 
I am really sorry for sending the message several time. I thought there 
was a problem with the way it was formatted or some such, hence why I 
sent it several times, because none of the messages seemed to get through.
So yeah, real sorry about that bit, and thanking you all

Gabriel C a écrit :
> Am So., 23. Dez. 2018 um 00:02 Uhr schrieb Linus Torvalds
> <torvalds@...ux-foundation.org>:
>>
>> On Sat, Dec 22, 2018 at 2:49 PM Christian Brauner
>> <christian.brauner@...onical.com> wrote:
>>>
>>> To be fair, no one apart from me was pointing out that it actually
>>> breaks people including systemd folks
>>> even though I was bringing it up with them. I even tried to fix all of
>>> userspace after this got NACKED
>>
>> Seriously, the "we don't break user space" is the #1 rule in the
>> kernel, and people should _know_ it's the #1 rule.
>>
>> If somebody ignores that rule, it needs to be escalated to me.
>> Immediately. Because I need to know.
>>
> 
> I do that usually but I didn't saw Christian's revert the time and I
> never hit that issue.
> Just saw that now because the unusual  [BREAKAGE] prefix.
> 
>> I need to know so that I can override the bogus NAK, and so that we
>> can fix the breakage ASAP. The absolute last thing we need is some
>> other user space then starting to rely on the new behavior, which just
>> compounds the problem and makes it a *much* bigger problem.
>>
> 
> Yes and you are right ..
> https://github.com/lxc/lxc/pull/2438
> 
> I've added an comment there about 4.20.0.
> 
> BR,
> 
> Gabriel
>