Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755445AbaG3MeS (ORCPT ); Wed, 30 Jul 2014 08:34:18 -0400 Received: from ip4-83-240-18-248.cust.nbox.cz ([83.240.18.248]:36716 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752884AbaG3MPc (ORCPT ); Wed, 30 Jul 2014 08:15:32 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Eric Dumazet , Steffen Klassert , "David S. Miller" , Jiri Slaby Subject: [PATCH 3.12 39/94] ipv4: irq safe sk_dst_[re]set() and ipv4_sk_update_pmtu() fix Date: Wed, 30 Jul 2014 14:14:28 +0200 Message-Id: <8728b0c1932dada25f2d1ccfa1669b5b41fe7937.1406722270.git.jslaby@suse.cz> X-Mailer: git-send-email 2.0.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet 3.12-stable review patch. If anyone has any objections, please let me know. =============== [ Upstream commit 7f502361531e9eecb396cf99bdc9e9a59f7ebd7f ] We have two different ways to handle changes to sk->sk_dst First way (used by TCP) assumes socket lock is owned by caller, and use no extra lock : __sk_dst_set() & __sk_dst_reset() Another way (used by UDP) uses sk_dst_lock because socket lock is not always taken. Note that sk_dst_lock is not softirq safe. These ways are not inter changeable for a given socket type. ipv4_sk_update_pmtu(), added in linux-3.8, added a race, as it used the socket lock as synchronization, but users might be UDP sockets. Instead of converting sk_dst_lock to a softirq safe version, use xchg() as we did for sk_rx_dst in commit e47eb5dfb296b ("udp: ipv4: do not use sk_dst_lock from softirq context") In a follow up patch, we probably can remove sk_dst_lock, as it is only used in IPv6. Signed-off-by: Eric Dumazet Cc: Steffen Klassert Fixes: 9cb3a50c5f63e ("ipv4: Invalidate the socket cached route on pmtu events if possible") Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby --- include/net/sock.h | 12 ++++++------ net/ipv4/route.c | 15 ++++++++------- 2 files changed, 14 insertions(+), 13 deletions(-) diff --git a/include/net/sock.h b/include/net/sock.h index dc84ec518ff5..def541a583de 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1789,9 +1789,11 @@ __sk_dst_set(struct sock *sk, struct dst_entry *dst) static inline void sk_dst_set(struct sock *sk, struct dst_entry *dst) { - spin_lock(&sk->sk_dst_lock); - __sk_dst_set(sk, dst); - spin_unlock(&sk->sk_dst_lock); + struct dst_entry *old_dst; + + sk_tx_queue_clear(sk); + old_dst = xchg(&sk->sk_dst_cache, dst); + dst_release(old_dst); } static inline void @@ -1803,9 +1805,7 @@ __sk_dst_reset(struct sock *sk) static inline void sk_dst_reset(struct sock *sk) { - spin_lock(&sk->sk_dst_lock); - __sk_dst_reset(sk); - spin_unlock(&sk->sk_dst_lock); + sk_dst_set(sk, NULL); } extern struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie); diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 2b681867164d..310963d7c028 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1032,20 +1032,21 @@ void ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu) const struct iphdr *iph = (const struct iphdr *) skb->data; struct flowi4 fl4; struct rtable *rt; - struct dst_entry *dst; + struct dst_entry *odst = NULL; bool new = false; bh_lock_sock(sk); - rt = (struct rtable *) __sk_dst_get(sk); + odst = sk_dst_get(sk); - if (sock_owned_by_user(sk) || !rt) { + if (sock_owned_by_user(sk) || !odst) { __ipv4_sk_update_pmtu(skb, sk, mtu); goto out; } __build_flow_key(&fl4, sk, iph, 0, 0, 0, 0, 0); - if (!__sk_dst_check(sk, 0)) { + rt = (struct rtable *)odst; + if (odst->obsolete && odst->ops->check(odst, 0) == NULL) { rt = ip_route_output_flow(sock_net(sk), &fl4, sk); if (IS_ERR(rt)) goto out; @@ -1055,8 +1056,7 @@ void ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu) __ip_rt_update_pmtu((struct rtable *) rt->dst.path, &fl4, mtu); - dst = dst_check(&rt->dst, 0); - if (!dst) { + if (!dst_check(&rt->dst, 0)) { if (new) dst_release(&rt->dst); @@ -1068,10 +1068,11 @@ void ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu) } if (new) - __sk_dst_set(sk, &rt->dst); + sk_dst_set(sk, &rt->dst); out: bh_unlock_sock(sk); + dst_release(odst); } EXPORT_SYMBOL_GPL(ipv4_sk_update_pmtu); -- 2.0.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/