linux-kernel - Re: net/sctp: vmalloc allocation failure in sctp_setsockopt/xt_alloc_table

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Message-ID: <20161128181803.GA13159@localhost.localdomain>
Date:   Mon, 28 Nov 2016 16:18:03 -0200
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Florian Westphal <fw@...len.de>
Cc:     Neil Horman <nhorman@...driver.com>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        netfilter-devel@...r.kernel.org
Subject: Re: net/sctp: vmalloc allocation failure in
 sctp_setsockopt/xt_alloc_table_info

On Mon, Nov 28, 2016 at 07:09:25PM +0100, Florian Westphal wrote:
> Neil Horman <nhorman@...driver.com> wrote:
> 
> [ trimming CCs ]
> 
> > On Mon, Nov 28, 2016 at 06:47:10PM +0100, Florian Westphal wrote:
> > > Neil Horman <nhorman@...driver.com> wrote:
> > > > I'm not sure I agree with that.  Generally speaking it seems like the right
> > > > thing to do, if you want to avoid filling logs with warnings, but this is the
> > > > sort of error that is going to be accompanied by severe service interruption.
> > > > I'd rather see a reason behind that in the logs, than just have it occur
> > > > silently.
> > > 
> > > Its not silent -- the setsockopt call will fail and userspace should
> > > display an error.
> > > 
> > Thats not true.  If the OOM succedes in freeing enough memory to fulfill the
> > request the setsockopt may complete without error, you're just left with a
> > killed process...somewhere.  Thats seems a bit dodgy to me
> 

__GFP_NOWARN is about allocation failures only and it won't disable OOM
kill messages.  oom_kill_process() has no idea on GFP_NOWARN when doing
the logging.

> We should prevent OOM killer from running in first place (GFP_NORETRY should work).

Oh. Really?