netdev - Re: [PATCH net] rxrpc: fix race condition in rxrpc_input

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Message-ID: <21268.1556038528@warthog.procyon.org.uk>
Date:   Tue, 23 Apr 2019 17:55:28 +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 net] rxrpc: fix race condition in rxrpc_input_packet()

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

> @@ -1181,6 +1177,9 @@ int rxrpc_input_packet(struct sock *udp_sk, struct sk_buff *skb)
>  
>  	_enter("%p", udp_sk);
>  
> +	if (!local)
> +		return -ENOENT;
> +
>  

This looks wrong.  Did you mean "return -AF_INET"?

The comment in net/ipv6/udp.c says:

		/*
		 * This is an encapsulation socket so pass the skb to
		 * the socket's udp_encap_rcv() hook. Otherwise, just
		 * fall through and pass this up the UDP socket.
		 * up->encap_rcv() returns the following value:
		 * =0 if skb was successfully passed to the encap
		 *    handler or was discarded by it.
		 * >0 if skb should be passed on to UDP.
		 * <0 if skb should be resubmitted as proto -N
		 */

This suggests that -ENOENT is not a valid return.  Should you "goto discard"
instead - or just discard the packet and return 0?

David