From mboxrd@z Thu Jan 1 00:00:00 1970 From: Soheil Hassas Yeganeh Subject: [PATCH net-next] sock: reset sk_err for ICMP packets read from error queue Date: Wed, 30 Nov 2016 14:01:08 -0500 Message-ID: <1480532468-1610-1-git-send-email-soheil.kdev@gmail.com> Cc: edumazet@google.com, willemb@google.com, maze@google.com, hannes@stressinduktion.org, Soheil Hassas Yeganeh To: davem@davemloft.net, netdev@vger.kernel.org Return-path: Received: from mail-qt0-f193.google.com ([209.85.216.193]:35577 "EHLO mail-qt0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755486AbcK3TBR (ORCPT ); Wed, 30 Nov 2016 14:01:17 -0500 Received: by mail-qt0-f193.google.com with SMTP id m48so20730155qta.2 for ; Wed, 30 Nov 2016 11:01:17 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: From: Soheil Hassas Yeganeh Only when ICMP packets are enqueued onto the error queue, sk_err is also set. Before f5f99309fa74 (sock: do not set sk_err in sock_dequeue_err_skb), a subsequent error queue read would set sk_err to the next error on the queue, or 0 if empty. As no error types other than ICMP set this field, sk_err should not be modified upon dequeuing them. Only for ICMP errors, reset the (racy) sk_err. Some applications, like traceroute, rely on it and go into a futile busy POLLERR loop otherwise. In principle, sk_err has to be set while an ICMP error is queued. Testing is_icmp_err_skb(skb_next) approximates this without requiring a full queue walk. Applications that receive both ICMP and other errors cannot rely on this legacy behavior, as other errors do not set sk_err in the first place. Fixes: f5f99309fa74 (sock: do not set sk_err in sock_dequeue_err_skb) Signed-off-by: Soheil Hassas Yeganeh Signed-off-by: Willem de Bruijn --- net/core/skbuff.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index d1d1a5a..8dad391 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3714,20 +3714,29 @@ int sock_queue_err_skb(struct sock *sk, struct sk_buff *skb) } EXPORT_SYMBOL(sock_queue_err_skb); +static bool is_icmp_err_skb(const struct sk_buff *skb) +{ + return skb && (SKB_EXT_ERR(skb)->ee.ee_origin == SO_EE_ORIGIN_ICMP || + SKB_EXT_ERR(skb)->ee.ee_origin == SO_EE_ORIGIN_ICMP6); +} + struct sk_buff *sock_dequeue_err_skb(struct sock *sk) { struct sk_buff_head *q = &sk->sk_error_queue; - struct sk_buff *skb, *skb_next; + struct sk_buff *skb, *skb_next = NULL; + bool icmp_next = false; unsigned long flags; - int err = 0; spin_lock_irqsave(&q->lock, flags); skb = __skb_dequeue(q); if (skb && (skb_next = skb_peek(q))) - err = SKB_EXT_ERR(skb_next)->ee.ee_errno; + icmp_next = is_icmp_err_skb(skb_next); spin_unlock_irqrestore(&q->lock, flags); - if (err) + if (is_icmp_err_skb(skb) && !icmp_next) + sk->sk_err = 0; + + if (skb_next) sk->sk_error_report(sk); return skb; -- 2.8.0.rc3.226.g39d4020