netdev - Re: [PATCH net] tcp: fix potential huge kmalloc() calls in TCP

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Message-ID: <1447935955.22599.195.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Thu, 19 Nov 2015 04:25:55 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Pavel Emelyanov <xemul@...allels.com>
Cc:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] tcp: fix potential huge kmalloc() calls in
 TCP_REPAIR

On Thu, 2015-11-19 at 13:51 +0300, Pavel Emelyanov wrote:
> On 11/19/2015 08:03 AM, Eric Dumazet wrote:
> > From: Eric Dumazet <edumazet@...gle.com>
> > 
> > tcp_send_rcvq() is used for re-injecting data into tcp receive queue.
> > 
> > Problems :
> > 
> > - No check against size is performed, allowed user to fool kernel in
> >   attempting very large memory allocations, eventually triggering
> >   OOM when memory is fragmented.
> 
> Doesn't the tcp_try_rmem_schedule() protect us from doing this "eventually"?
> I mean first we would be allowed to do it, but then the sock will be charged
> with the previous allocations and will not add more memory to socket.

But this tcp_try_rmem_schedule() is done _after_ allocation was
attempted. This is too late :(



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