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

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Date:   Wed, 30 Nov 2016 17:21:45 -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 04:18:03PM -0200, Marcelo Ricardo Leitner wrote:
> 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?
> 

Now I see why. Then we're basically saying that's better to fail this
operation than to kill some random process around.
And kmalloc() is already using GFP_NORETRY in this same place.

  Marcelo