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

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Message-ID: <20180129182521.GI21609@dhcp22.suse.cz>
Date:   Mon, 29 Jan 2018 19:25:21 +0100
From:   Michal Hocko <mhocko@...nel.org>
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,
        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 Mon 29-01-18 17:57:22, Florian Westphal wrote:
> Kirill A. Shutemov <kirill@...temov.name> wrote:
> > On Mon, Jan 29, 2018 at 08:23:57AM +0100, 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.
> 
> Isn't that what we do everywhere in network stack?
> 
> 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.

If this is a root only thing then __GFP_NORETRY sounds like the most
straightforward way to go.
-- 
Michal Hocko
SUSE Labs