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

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Date:   Mon, 29 Jan 2018 19:24:01 +0100 (CET)
From:   Jan Engelhardt <jengelh@...i.de>
To:     Florian Westphal <fw@...len.de>
cc:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        davem@...emloft.net, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, netdev@...r.kernel.org,
        aarcange@...hat.com, yang.s@...baba-inc.com, mhocko@...e.com,
        syzkaller-bugs@...glegroups.com, linux-kernel@...r.kernel.org,
        mingo@...nel.org, linux-mm@...ck.org, rientjes@...gle.com,
        akpm@...ux-foundation.org, guro@...com,
        kirill.shutemov@...ux.intel.com
Subject: Re: [netfilter-core] kernel panic: Out of memory and no killable
 processes... (2)


On Monday 2018-01-29 17:57, Florian Westphal wrote:
>> > > vmalloc() once became killable by commit 5d17a73a2ebeb8d1 ("vmalloc: back
>> > > off when the current task is killed") but then became unkillable by commit
>> > > b8c8a338f75e052d ("Revert "vmalloc: back off when the current task is
>> > > killed""). Therefore, we can't handle this problem from MM side.
>> > > Please consider adding some limit from networking side.
>> > 
>> > I don't know what "some limit" would be.  I would prefer if there was
>> > a way to supress OOM Killer in first place so we can just -ENOMEM user.
>> 
>> Just supressing OOM kill is a bad idea. We still leave a way to allocate
>> arbitrary large buffer in kernel.

At the very least, mm could limit that kind of "arbitrary". If the machine has
x GB (swap included) and the admin tries to make the kernel allocate space for
an x GB ruleset, no way is it going to be satisfiable _even with OOM_.

>I think we should try to allocate whatever amount of memory is needed
>for the given xtables ruleset, given that is what admin requested us to do.