From 83a1a1a70e87f676fbb6086b26b6ac7f7fdd107d Mon Sep 17 00:00:00 2001 From: Soheil Hassas Yeganeh Date: Wed, 30 Nov 2016 14:01:08 -0500 Subject: [PATCH] sock: reset sk_err for ICMP packets read from error queue MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Acked-by: Eric Dumazet Acked-by: Maciej Żenczykowski Signed-off-by: David S. Miller --- 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 ea6fa954c7a0..b45cd1494243 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; -- 2.30.2