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Date:   Tue, 23 Apr 2019 23:06:39 +0100
From:   David Howells <dhowells@...hat.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     dhowells@...hat.com, "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH v2 net] rxrpc: fix race condition in rxrpc_input_packet()

Eric Dumazet <edumazet@...gle.com> wrote:

> @@ -1161,19 +1161,15 @@ int rxrpc_extract_header(struct rxrpc_skb_priv *sp, struct sk_buff *skb)
>   * handle data received on the local endpoint
>   * - may be called in interrupt context
>   *
> - * The socket is locked by the caller and this prevents the socket from being
> - * shut down and the local endpoint from going away, thus sk_user_data will not
> - * be cleared until this function returns.
> - *

I'd prefer not to remove the comment entirely.  Could it be changed to:

 * [!] Note that as this is called from the encap_rcv hook, the socket is not
 * held locked by the caller and nothing prevents sk_user_data on the UDP from
 * being cleared in the middle of processing this function.

> @@ -1181,6 +1177,10 @@ int rxrpc_input_packet(struct sock *udp_sk, struct sk_buff *skb)
>  
>  	_enter("%p", udp_sk);
>  
> +	if (unlikely(!local)) {
> +		kfree_skb(skb);
> +		return 0;
> +	}

This looks better, thanks.

David

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