netdev - Re: [PATCH net v2] tcp/dccp: fix possible race __inet_lookup

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Date:   Fri, 13 Dec 2019 21:45:22 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Michal Kubecek <mkubecek@...e.cz>,
        Firo Yang <firo.yang@...e.com>
Subject: Re: [PATCH net v2] tcp/dccp: fix possible race
 __inet_lookup_established()

On Fri, 13 Dec 2019 18:20:41 -0800, Eric Dumazet wrote:
> Michal Kubecek and Firo Yang did a very nice analysis of crashes
> happening in __inet_lookup_established().
> 
> Since a TCP socket can go from TCP_ESTABLISH to TCP_LISTEN
> (via a close()/socket()/listen() cycle) without a RCU grace period,
> I should not have changed listeners linkage in their hash table.
> 
> They must use the nulls protocol (Documentation/RCU/rculist_nulls.txt),
> so that a lookup can detect a socket in a hash list was moved in
> another one.
> 
> Since we added code in commit d296ba60d8e2 ("soreuseport: Resolve
> merge conflict for v4/v6 ordering fix"), we have to add
> hlist_nulls_add_tail_rcu() helper.
> 
> Fixes: 3b24d854cb35 ("tcp/dccp: do not touch listener sk_refcnt under synflood")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Michal Kubecek <mkubecek@...e.cz>
> Reported-by: Firo Yang <firo.yang@...e.com>
> Reviewed-by: Michal Kubecek <mkubecek@...e.cz>
> Link: https://lore.kernel.org/netdev/20191120083919.GH27852@unicorn.suse.cz/

Applied, and queued for stable, thank you!