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

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Date:   Thu, 27 Jul 2017 06:35:39 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Sam Edwards <CFSworks@...il.com>,
        Marc Haber <mh+netdev@...schlus.de>,
        Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>
Subject: Re: [PATCH net] udp6: fix socket leak on early demux

On Thu, 2017-07-27 at 14:45 +0200, Paolo Abeni wrote:
> 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>
> ---

Acked-by: Eric Dumazet <edumazet@...gle.com>