From c0a11493ee6141d475fc96cf3ba24441299c9f16 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 27 Aug 2024 01:52:50 +0000 Subject: [PATCH] tcp: annotate data-races around tcptw->tw_rcv_nxt No lock protects tcp tw fields. tcptw->tw_rcv_nxt can be changed from twsk_rcv_nxt_update() while other threads might read this field. Add READ_ONCE()/WRITE_ONCE() annotations, and make sure tcp_timewait_state_process() reads tcptw->tw_rcv_nxt only once. Signed-off-by: Eric Dumazet Reviewed-by: Jason Xing Link: https://patch.msgid.link/20240827015250.3509197-3-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/ipv4/tcp_ipv4.c | 2 +- net/ipv4/tcp_minisocks.c | 27 +++++++++++++++------------ net/ipv6/tcp_ipv6.c | 3 ++- 3 files changed, 18 insertions(+), 14 deletions(-) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 7c29158e1abc..eb631e66ee03 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1073,7 +1073,7 @@ static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb) } tcp_v4_send_ack(sk, skb, - tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt, + tcptw->tw_snd_nxt, READ_ONCE(tcptw->tw_rcv_nxt), tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale, tcp_tw_tsval(tcptw), READ_ONCE(tcptw->tw_ts_recent), diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index b6d547d29f9a..ad562272db2e 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -52,16 +52,17 @@ tcp_timewait_check_oow_rate_limit(struct inet_timewait_sock *tw, return TCP_TW_SUCCESS; } -static void twsk_rcv_nxt_update(struct tcp_timewait_sock *tcptw, u32 seq) +static void twsk_rcv_nxt_update(struct tcp_timewait_sock *tcptw, u32 seq, + u32 rcv_nxt) { #ifdef CONFIG_TCP_AO struct tcp_ao_info *ao; ao = rcu_dereference(tcptw->ao_info); - if (unlikely(ao && seq < tcptw->tw_rcv_nxt)) + if (unlikely(ao && seq < rcv_nxt)) WRITE_ONCE(ao->rcv_sne, ao->rcv_sne + 1); #endif - tcptw->tw_rcv_nxt = seq; + WRITE_ONCE(tcptw->tw_rcv_nxt, seq); } /* @@ -98,8 +99,9 @@ enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, const struct tcphdr *th, u32 *tw_isn) { - struct tcp_options_received tmp_opt; struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw); + u32 rcv_nxt = READ_ONCE(tcptw->tw_rcv_nxt); + struct tcp_options_received tmp_opt; bool paws_reject = false; int ts_recent_stamp; @@ -123,20 +125,20 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, /* Out of window, send ACK */ if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq, - tcptw->tw_rcv_nxt, - tcptw->tw_rcv_nxt + tcptw->tw_rcv_wnd)) + rcv_nxt, + rcv_nxt + tcptw->tw_rcv_wnd)) return tcp_timewait_check_oow_rate_limit( tw, skb, LINUX_MIB_TCPACKSKIPPEDFINWAIT2); if (th->rst) goto kill; - if (th->syn && !before(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt)) + if (th->syn && !before(TCP_SKB_CB(skb)->seq, rcv_nxt)) return TCP_TW_RST; /* Dup ACK? */ if (!th->ack || - !after(TCP_SKB_CB(skb)->end_seq, tcptw->tw_rcv_nxt) || + !after(TCP_SKB_CB(skb)->end_seq, rcv_nxt) || TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) { inet_twsk_put(tw); return TCP_TW_SUCCESS; @@ -146,12 +148,13 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, * reset. */ if (!th->fin || - TCP_SKB_CB(skb)->end_seq != tcptw->tw_rcv_nxt + 1) + TCP_SKB_CB(skb)->end_seq != rcv_nxt + 1) return TCP_TW_RST; /* FIN arrived, enter true time-wait state. */ WRITE_ONCE(tw->tw_substate, TCP_TIME_WAIT); - twsk_rcv_nxt_update(tcptw, TCP_SKB_CB(skb)->end_seq); + twsk_rcv_nxt_update(tcptw, TCP_SKB_CB(skb)->end_seq, + rcv_nxt); if (tmp_opt.saw_tstamp) { WRITE_ONCE(tcptw->tw_ts_recent_stamp, @@ -182,7 +185,7 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, */ if (!paws_reject && - (TCP_SKB_CB(skb)->seq == tcptw->tw_rcv_nxt && + (TCP_SKB_CB(skb)->seq == rcv_nxt && (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq || th->rst))) { /* In window segment, it may be only reset or bare ack. */ @@ -229,7 +232,7 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, */ if (th->syn && !th->rst && !th->ack && !paws_reject && - (after(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt) || + (after(TCP_SKB_CB(skb)->seq, rcv_nxt) || (tmp_opt.saw_tstamp && (s32)(READ_ONCE(tcptw->tw_ts_recent) - tmp_opt.rcv_tsval) < 0))) { u32 isn = tcptw->tw_snd_nxt + 65535 + 2; diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index fb2e64ce660f..d71ab4e1efe1 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1193,7 +1193,8 @@ static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb) #endif } - tcp_v6_send_ack(sk, skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt, + tcp_v6_send_ack(sk, skb, tcptw->tw_snd_nxt, + READ_ONCE(tcptw->tw_rcv_nxt), tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale, tcp_tw_tsval(tcptw), READ_ONCE(tcptw->tw_ts_recent), tw->tw_bound_dev_if,