linux-kernel - Re: [PATCH 3.16 08/10] tcp: tcp_fragment() should apply sane memory limits

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Date:   Mon, 1 Jul 2019 19:51:10 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Ben Hutchings <ben@...adent.org.uk>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Jonathan Looney <jtl@...flix.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Tyler Hicks <tyhicks@...onical.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Bruce Curtis <brucec@...flix.com>
Subject: Re: [PATCH 3.16 08/10] tcp: tcp_fragment() should apply sane memory
 limits

Hi Ben,

On 6/18/2019 7:28 AM, Ben Hutchings wrote:
> 3.16.69-rc1 review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Eric Dumazet <edumazet@...gle.com>
> 
> commit f070ef2ac66716357066b683fb0baf55f8191a2e upstream.
> 
> Jonathan Looney reported that a malicious peer can force a sender
> to fragment its retransmit queue into tiny skbs, inflating memory
> usage and/or overflow 32bit counters.
> 
> TCP allows an application to queue up to sk_sndbuf bytes,
> so we need to give some allowance for non malicious splitting
> of retransmit queue.
> 
> A new SNMP counter is added to monitor how many times TCP
> did not allow to split an skb if the allowance was exceeded.
> 
> Note that this counter might increase in the case applications
> use SO_SNDBUF socket option to lower sk_sndbuf.
> 
> CVE-2019-11478 : tcp_fragment, prevent fragmenting a packet when the
> 	socket is already using more than half the allowed space
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Jonathan Looney <jtl@...flix.com>
> Acked-by: Neal Cardwell <ncardwell@...gle.com>
> Acked-by: Yuchung Cheng <ycheng@...gle.com>
> Reviewed-by: Tyler Hicks <tyhicks@...onical.com>
> Cc: Bruce Curtis <brucec@...flix.com>
> Cc: Jonathan Lemon <jonathan.lemon@...il.com>
> Signed-off-by: David S. Miller <davem@...emloft.net>
> [Salvatore Bonaccorso: Adjust context for backport to 4.9.168]
> [bwh: Backported to 3.16: adjust context]
> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>

Don't we also need this patch to be backported:

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b6653b3629e5b88202be3c9abc44713973f5c4b4

Thanks!
-- 
Florian