netdev - Re: [PATCH net] udp6: fix socket leak on early demux

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Date:   Sat, 29 Jul 2017 14:19:43 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     pabeni@...hat.com
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, CFSworks@...il.com,
        mh+netdev@...schlus.de, subashab@...eaurora.org
Subject: Re: [PATCH net] udp6: fix socket leak on early demux

From: Paolo Abeni <pabeni@...hat.com>
Date: Thu, 27 Jul 2017 14:45:09 +0200

> When an early demuxed packet reaches __udp6_lib_lookup_skb(), the
> sk reference is retrieved and used, but the relevant reference
> count is leaked and the socket destructor is never called.
> Beyond leaking the sk memory, if there are pending UDP packets
> in the receive queue, even the related accounted memory is leaked.
> 
> In the long run, this will cause persistent forward allocation errors
> and no UDP skbs (both ipv4 and ipv6) will be able to reach the
> user-space.
> 
> Fix this by explicitly accessing the early demux reference before
> the lookup, and properly decreasing the socket reference count
> after usage.
> 
> Also drop the skb_steal_sock() in __udp6_lib_lookup_skb(), and
> the now obsoleted comment about "socket cache".
> 
> The newly added code is derived from the current ipv4 code for the
> similar path.
> 
> v1 -> v2:
>   fixed the __udp6_lib_rcv() return code for resubmission,
>   as suggested by Eric
> 
> Reported-by: Sam Edwards <CFSworks@...il.com>
> Reported-by: Marc Haber <mh+netdev@...schlus.de>
> Fixes: 5425077d73e0 ("net: ipv6: Add early demux handler for UDP unicast")
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Applied.