netdev - Re: [PATCH net] udp: fix dst races with multicast early demux

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Date:	Mon, 03 Aug 2015 22:20:57 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	Gregory.Hoggarth@...iedtelesis.co.nz, sbohrer@...advisors.com,
	netdev@...r.kernel.org, alexgartrell@...il.com, mkubecek@...e.cz
Subject: Re: [PATCH net] udp: fix dst races with multicast early demux

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sat, 01 Aug 2015 12:14:33 +0200

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Multicast dst are not cached. They carry DST_NOCACHE.
> 
> As mentioned in commit f8864972126899 ("ipv4: fix dst race in
> sk_dst_get()"), these dst need special care before caching them
> into a socket.
> 
> Caching them is allowed only if their refcnt was not 0, ie we
> must use atomic_inc_not_zero()
> 
> Also, we must use READ_ONCE() to fetch sk->sk_rx_dst, as mentioned
> in commit d0c294c53a771 ("tcp: prevent fetching dst twice in early demux
> code")
> 
> Fixes: 421b3885bf6d ("udp: ipv4: Add udp early demux")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Gregory Hoggarth <Gregory.Hoggarth@...iedtelesis.co.nz>
> Reported-by: Alex Gartrell <agartrell@...com>
> Cc: Michal Kubeček <mkubecek@...e.cz>
> ---
> David : I will be on vacation for following 7 days, no internet access.
> Please wait for tests done by Gregory & Alex before merging this ?
> Thanks !

Now that this has been tested by Gregory, applied and queued up for
-stable thanks!
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