From 556574d97b6e0c2970b7e5ab693bcf35f73195fa Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 30 May 2015 09:16:53 -0700 Subject: udp: fix behavior of wrong checksums commit beb39db59d14990e401e235faf66a6b9b31240b0 upstream. We have two problems in UDP stack related to bogus checksums : 1) We return -EAGAIN to application even if receive queue is not empty. This breaks applications using edge trigger epoll() 2) Under UDP flood, we can loop forever without yielding to other processes, potentially hanging the host, especially on non SMP. This patch is an attempt to make things better. We might in the future add extra support for rt applications wanting to better control time spent doing a recv() in a hostile environment. For example we could validate checksums before queuing packets in socket receive queue. Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/ipv4/udp.c | 6 ++---- net/ipv6/udp.c | 6 ++---- 2 files changed, 4 insertions(+), 8 deletions(-) (limited to 'net') diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 8c2e259..5e92043 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1248,10 +1248,8 @@ csum_copy_err: UDP_INC_STATS_USER(sock_net(sk), UDP_MIB_INERRORS, is_udplite); unlock_sock_fast(sk, slow); - if (noblock) - return -EAGAIN; - - /* starting over for a new packet */ + /* starting over for a new packet, but check if we need to yield */ + cond_resched(); msg->msg_flags &= ~MSG_TRUNC; goto try_again; } diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index d131a95..dc08afd 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -451,10 +451,8 @@ csum_copy_err: } unlock_sock_fast(sk, slow); - if (noblock) - return -EAGAIN; - - /* starting over for a new packet */ + /* starting over for a new packet, but check if we need to yield */ + cond_resched(); msg->msg_flags &= ~MSG_TRUNC; goto try_again; } -- cgit v1.1