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sock: reset sk_err for ICMP packets read from error queue

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Only when ICMP packets are enqueued onto the error queue,
sk_err is also set. Before f5f99309fa (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: f5f99309fa (sock: do not set sk_err in sock_dequeue_err_skb)
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Soheil Hassas Yeganeh
2016-11-30 14:01:08 -05:00
committed by David S. Miller
parent f577e22c73
commit 83a1a1a70e
1 changed files with 13 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
net/core/skbuff.c
View File

@@ -3714,20 +3714,29 @@ int sock_queue_err_skb(struct sock *sk, struct sk_buff *skb)
} }
EXPORT_SYMBOL(sock_queue_err_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 *sock_dequeue_err_skb(struct sock *sk)
{ {
struct sk_buff_head *q = &sk->sk_error_queue; 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; unsigned long flags;
int err = 0;
spin_lock_irqsave(&q->lock, flags); spin_lock_irqsave(&q->lock, flags);
skb = __skb_dequeue(q); skb = __skb_dequeue(q);
if (skb && (skb_next = skb_peek(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); 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); sk->sk_error_report(sk);
return skb; return skb;