| From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> |
| Date: Mon, 21 Aug 2017 15:09:13 +0200 |
| Subject: [PATCH] net: take the tcp_sk_lock lock with BH disabled |
| |
| Lockdep may complain about an unsafe locking scenario: |
| | CPU0 CPU1 |
| | ---- ---- |
| | lock((tcp_sk_lock).lock); |
| | lock(&per_cpu(local_softirq_locks[i], __cpu).lock); |
| | lock((tcp_sk_lock).lock); |
| | lock(&per_cpu(local_softirq_locks[i], __cpu).lock); |
| |
| in the call paths: |
| do_current_softirqs -> tcp_v4_send_ack() |
| vs |
| tcp_v4_send_reset -> do_current_softirqs(). |
| |
| This should not happen since local_softirq_locks is per CPU. Reversing |
| the order makes lockdep happy. |
| |
| Reported-by: Jacek Konieczny <jajcus@jajcus.net> |
| Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> |
| --- |
| net/ipv4/tcp_ipv4.c | 8 ++++---- |
| 1 file changed, 4 insertions(+), 4 deletions(-) |
| |
| --- a/net/ipv4/tcp_ipv4.c |
| +++ b/net/ipv4/tcp_ipv4.c |
| @@ -713,8 +713,8 @@ static void tcp_v4_send_reset(const stru |
| |
| arg.tos = ip_hdr(skb)->tos; |
| arg.uid = sock_net_uid(net, sk && sk_fullsock(sk) ? sk : NULL); |
| - local_lock(tcp_sk_lock); |
| local_bh_disable(); |
| + local_lock(tcp_sk_lock); |
| ip_send_unicast_reply(*this_cpu_ptr(net->ipv4.tcp_sk), |
| skb, &TCP_SKB_CB(skb)->header.h4.opt, |
| ip_hdr(skb)->saddr, ip_hdr(skb)->daddr, |
| @@ -722,8 +722,8 @@ static void tcp_v4_send_reset(const stru |
| |
| __TCP_INC_STATS(net, TCP_MIB_OUTSEGS); |
| __TCP_INC_STATS(net, TCP_MIB_OUTRSTS); |
| - local_bh_enable(); |
| local_unlock(tcp_sk_lock); |
| + local_bh_enable(); |
| |
| #ifdef CONFIG_TCP_MD5SIG |
| out: |
| @@ -801,16 +801,16 @@ static void tcp_v4_send_ack(const struct |
| arg.bound_dev_if = oif; |
| arg.tos = tos; |
| arg.uid = sock_net_uid(net, sk_fullsock(sk) ? sk : NULL); |
| - local_lock(tcp_sk_lock); |
| local_bh_disable(); |
| + local_lock(tcp_sk_lock); |
| ip_send_unicast_reply(*this_cpu_ptr(net->ipv4.tcp_sk), |
| skb, &TCP_SKB_CB(skb)->header.h4.opt, |
| ip_hdr(skb)->saddr, ip_hdr(skb)->daddr, |
| &arg, arg.iov[0].iov_len); |
| |
| __TCP_INC_STATS(net, TCP_MIB_OUTSEGS); |
| - local_bh_enable(); |
| local_unlock(tcp_sk_lock); |
| + local_bh_enable(); |
| } |
| |
| static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb) |