netdev - Re: [PATCH net] net: Unpublish sk from sk_reuseport_cb before call

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Date:   Mon, 30 Sep 2019 17:14:32 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     kafai@...com
Cc:     netdev@...r.kernel.org, kernel-team@...com, eric.dumazet@...il.com
Subject: Re: [PATCH net] net: Unpublish sk from sk_reuseport_cb before
 call_rcu

From: Martin KaFai Lau <kafai@...com>
Date: Fri, 27 Sep 2019 16:00:31 -0700

> The "reuse->sock[]" array is shared by multiple sockets.  The going away
> sk must unpublish itself from "reuse->sock[]" before making call_rcu()
> call.  However, this unpublish-action is currently done after a grace
> period and it may cause use-after-free.
> 
> The fix is to move reuseport_detach_sock() to sk_destruct().
> Due to the above reason, any socket with sk_reuseport_cb has
> to go through the rcu grace period before freeing it.
> 
> It is a rather old bug (~3 yrs).  The Fixes tag is not necessary
> the right commit but it is the one that introduced the SOCK_RCU_FREE
> logic and this fix is depending on it.
> 
> Fixes: a4298e4522d6 ("net: add SOCK_RCU_FREE socket flag")
> Cc: Eric Dumazet <eric.dumazet@...il.com>
> Suggested-by: Eric Dumazet <eric.dumazet@...il.com>
> Signed-off-by: Martin KaFai Lau <kafai@...com>

Applied and queued up for -stable, thanks Martin.