netdev - Re: net: use-after-free in worker

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Message-ID: <20161205072140.GC9496@gondor.apana.org.au>
Date:   Mon, 5 Dec 2016 15:21:40 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Andrey Konovalov <andreyknvl@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Florian Westphal <fw@...len.de>,
        Eric Dumazet <edumazet@...gle.com>,
        Bob Copeland <me@...copeland.com>,
        Tom Herbert <tom@...bertland.com>,
        David Decotigny <decot@...glers.com>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kostya Serebryany <kcc@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net: use-after-free in worker_thread

On Sat, Dec 03, 2016 at 05:49:07AM -0800, Eric Dumazet wrote:
>
> @@ -600,6 +600,7 @@ static int __netlink_create(struct net *net, struct socket *sock,
>  	}
>  	init_waitqueue_head(&nlk->wait);
>  
> +	sock_set_flag(sk, SOCK_RCU_FREE);
>  	sk->sk_destruct = netlink_sock_destruct;
>  	sk->sk_protocol = protocol;
>  	return 0;

It's not necessarily a big deal but I just wanted to point out
that SOCK_RCU_FREE is not equivalent to the call_rcu thing that
netlink does.  The latter only does the RCU deferral for the socket
release call which is the only place where it's needed while
SOCK_RCU_FREE will force every path to do an RCU deferral.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt