netdev - Re: [netfilter-core] kernel panic: Out of memory and no killable processes... (2)

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Message-ID: <CACT4Y+bFKwoxopr1dwnc7OHUoHy28ksVguqtMY6tD=aRh-7LyQ@mail.gmail.com>
Date:   Tue, 30 Jan 2018 10:02:34 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Florian Westphal <fw@...len.de>, Michal Hocko <mhocko@...nel.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        David Miller <davem@...emloft.net>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev <netdev@...r.kernel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Yang Shi <yang.s@...baba-inc.com>,
        syzkaller-bugs@...glegroups.com,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>, Linux-MM <linux-mm@...ck.org>,
        David Rientjes <rientjes@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, guro@...com,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [netfilter-core] kernel panic: Out of memory and no killable
 processes... (2)

On Tue, Jan 30, 2018 at 9:28 AM, Kirill A. Shutemov
<kirill@...temov.name> wrote:
> On Tue, Jan 30, 2018 at 09:11:27AM +0100, Florian Westphal wrote:
>> Michal Hocko <mhocko@...nel.org> wrote:
>> > On Mon 29-01-18 23:35:22, Florian Westphal wrote:
>> > > Kirill A. Shutemov <kirill@...temov.name> wrote:
>> > [...]
>> > > > I hate what I'm saying, but I guess we need some tunable here.
>> > > > Not sure what exactly.
>> > >
>> > > Would memcg help?
>> >
>> > That really depends. I would have to check whether vmalloc path obeys
>> > __GFP_ACCOUNT (I suspect it does except for page tables allocations but
>> > that shouldn't be a big deal). But then the other potential problem is
>> > the life time of the xt_table_info (or other potentially large) data
>> > structures. Are they bound to any process life time.
>>
>> No.
>
> Well, IIUC they bound to net namespace life time, so killing all
> proccesses in the namespace would help to get memory back. :)

... unless the namespace is mounted into file system.

Let's start with NOWARN as that's what kernel generally uses for
allocations with user-controllable size. ENOMEM is roughly as
informative as the WARNING message in this case.

I think we also need to consider setting up memory cgroup for
syzkaller test processes (we do RLIMIT_AS, but that's weak).