From 404e0a8b6a55d5e1cd138c6deb1bca9abdf75d8c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 29 Jul 2012 23:20:37 +0000 Subject: net: ipv4: fix RCU races on dst refcounts commit c6cffba4ffa2 (ipv4: Fix input route performance regression.) added various fatal races with dst refcounts. crashes happen on tcp workloads if routes are added/deleted at the same time. The dst_free() calls from free_fib_info_rcu() are clearly racy. We need instead regular dst refcounting (dst_release()) and make sure dst_release() is aware of RCU grace periods : Add DST_RCU_FREE flag so that dst_release() respects an RCU grace period before dst destruction for cached dst Introduce a new inet_sk_rx_dst_set() helper, using atomic_inc_not_zero() to make sure we dont increase a zero refcount (On a dst currently waiting an rcu grace period before destruction) rt_cache_route() must take a reference on the new cached route, and release it if was not able to install it. With this patch, my machines survive various benchmarks. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/fib_semantics.c | 4 ++-- net/ipv4/route.c | 16 ++++------------ net/ipv4/tcp_input.c | 3 +-- net/ipv4/tcp_ipv4.c | 12 ++++++------ net/ipv4/tcp_minisocks.c | 3 +-- 5 files changed, 14 insertions(+), 24 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index da0cc2e6b250..e55171f184f9 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -172,9 +172,9 @@ static void free_fib_info_rcu(struct rcu_head *head) if (nexthop_nh->nh_exceptions) free_nh_exceptions(nexthop_nh); if (nexthop_nh->nh_rth_output) - dst_free(&nexthop_nh->nh_rth_output->dst); + dst_release(&nexthop_nh->nh_rth_output->dst); if (nexthop_nh->nh_rth_input) - dst_free(&nexthop_nh->nh_rth_input->dst); + dst_release(&nexthop_nh->nh_rth_input->dst); } endfor_nexthops(fi); release_net(fi->fib_net); diff --git a/net/ipv4/route.c b/net/ipv4/route.c index fc1a81ca79a7..d6eabcfe8a90 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1199,11 +1199,6 @@ restart: fnhe->fnhe_stamp = jiffies; } -static inline void rt_free(struct rtable *rt) -{ - call_rcu_bh(&rt->dst.rcu_head, dst_rcu_free); -} - static void rt_cache_route(struct fib_nh *nh, struct rtable *rt) { struct rtable *orig, *prev, **p = &nh->nh_rth_output; @@ -1213,17 +1208,14 @@ static void rt_cache_route(struct fib_nh *nh, struct rtable *rt) orig = *p; + rt->dst.flags |= DST_RCU_FREE; + dst_hold(&rt->dst); prev = cmpxchg(p, orig, rt); if (prev == orig) { if (orig) - rt_free(orig); + dst_release(&orig->dst); } else { - /* Routes we intend to cache in the FIB nexthop have - * the DST_NOCACHE bit clear. However, if we are - * unsuccessful at storing this route into the cache - * we really need to set it. - */ - rt->dst.flags |= DST_NOCACHE; + dst_release(&rt->dst); } } diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index a356e1fecf9a..9be30b039ae3 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5604,8 +5604,7 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb) tcp_set_state(sk, TCP_ESTABLISHED); if (skb != NULL) { - sk->sk_rx_dst = dst_clone(skb_dst(skb)); - inet_sk(sk)->rx_dst_ifindex = skb->skb_iif; + inet_sk_rx_dst_set(sk, skb); security_inet_conn_established(sk, skb); } diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 2fbd9921253f..7f91e5ac8277 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1617,19 +1617,19 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb) #endif if (sk->sk_state == TCP_ESTABLISHED) { /* Fast path */ + struct dst_entry *dst = sk->sk_rx_dst; + sock_rps_save_rxhash(sk, skb); - if (sk->sk_rx_dst) { - struct dst_entry *dst = sk->sk_rx_dst; + if (dst) { if (inet_sk(sk)->rx_dst_ifindex != skb->skb_iif || dst->ops->check(dst, 0) == NULL) { dst_release(dst); sk->sk_rx_dst = NULL; } } - if (unlikely(sk->sk_rx_dst == NULL)) { - sk->sk_rx_dst = dst_clone(skb_dst(skb)); - inet_sk(sk)->rx_dst_ifindex = skb->skb_iif; - } + if (unlikely(sk->sk_rx_dst == NULL)) + inet_sk_rx_dst_set(sk, skb); + if (tcp_rcv_established(sk, skb, tcp_hdr(skb), skb->len)) { rsk = sk; goto reset; diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 3f1cc2028edd..232a90c3ec86 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -387,8 +387,7 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, struct tcp_sock *oldtp = tcp_sk(sk); struct tcp_cookie_values *oldcvp = oldtp->cookie_values; - newsk->sk_rx_dst = dst_clone(skb_dst(skb)); - inet_sk(newsk)->rx_dst_ifindex = skb->skb_iif; + inet_sk_rx_dst_set(newsk, skb); /* TCP Cookie Transactions require space for the cookie pair, * as it differs for each connection. There is no need to -- cgit v1.2.3