Merge branch 'net-sk_err-lockless-annotate'

Eric Dumazet says:

====================
net: annotate lockless accesses to sk_err[_soft]

This patch series is inspired by yet another syzbot report.

Most poll() handlers are lockless and read sk->sk_err
while other cpus can change it.

Add READ_ONCE/WRITE_ONCE() to major/usual offenders.

More to come later.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

20 files changed, 63 insertions, 56 deletions

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index a9b14f81d655..bd786b3be5ec 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -601,7 +601,7 @@ static void lowcomms_error_report(struct sock *sk)
 				   "sk_err=%d/%d\n", dlm_our_nodeid(),
 				   con->nodeid, &inet->inet_daddr,
 				   ntohs(inet->inet_dport), sk->sk_err,
-				   sk->sk_err_soft);
+				   READ_ONCE(sk->sk_err_soft));
 		break;
 #if IS_ENABLED(CONFIG_IPV6)
 	case AF_INET6:
@@ -610,14 +610,15 @@ static void lowcomms_error_report(struct sock *sk)
 				   "dport %d, sk_err=%d/%d\n", dlm_our_nodeid(),
 				   con->nodeid, &sk->sk_v6_daddr,
 				   ntohs(inet->inet_dport), sk->sk_err,
-				   sk->sk_err_soft);
+				   READ_ONCE(sk->sk_err_soft));
 		break;
 #endif
 	default:
 		printk_ratelimited(KERN_ERR "dlm: node %d: socket error "
 				   "invalid socket family %d set, "
 				   "sk_err=%d/%d\n", dlm_our_nodeid(),
-				   sk->sk_family, sk->sk_err, sk->sk_err_soft);
+				   sk->sk_family, sk->sk_err,
+				   READ_ONCE(sk->sk_err_soft));
 		break;
 	}
 
diff --git a/net/atm/signaling.c b/net/atm/signaling.c
index 5de06ab8ed75..e70ae2c113f9 100644
--- a/net/atm/signaling.c
+++ b/net/atm/signaling.c
@@ -125,7 +125,7 @@ as_indicate_complete:
 		break;
 	case as_addparty:
 	case as_dropparty:
-		sk->sk_err_soft = -msg->reply;
+		WRITE_ONCE(sk->sk_err_soft, -msg->reply);
 					/* < 0 failure, otherwise ep_ref */
 		clear_bit(ATM_VF_WAITING, &vcc->flags);
 		break;
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index b780827f5e0a..3ab68415d121 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -177,7 +177,7 @@ static inline void dccp_do_pmtu_discovery(struct sock *sk,
 	 * for the case, if this connection will not able to recover.
 	 */
 	if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
-		sk->sk_err_soft = EMSGSIZE;
+		WRITE_ONCE(sk->sk_err_soft, EMSGSIZE);
 
 	mtu = dst_mtu(dst);
 
@@ -339,8 +339,9 @@ static int dccp_v4_err(struct sk_buff *skb, u32 info)
 			sk_error_report(sk);
 
 			dccp_done(sk);
-		} else
-			sk->sk_err_soft = err;
+		} else {
+			WRITE_ONCE(sk->sk_err_soft, err);
+		}
 		goto out;
 	}
 
@@ -364,8 +365,9 @@ static int dccp_v4_err(struct sk_buff *skb, u32 info)
 	if (!sock_owned_by_user(sk) && inet->recverr) {
 		sk->sk_err = err;
 		sk_error_report(sk);
-	} else /* Only an error on timeout */
-		sk->sk_err_soft = err;
+	} else { /* Only an error on timeout */
+		WRITE_ONCE(sk->sk_err_soft, err);
+	}
 out:
 	bh_unlock_sock(sk);
 	sock_put(sk);
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index b9d7c3dd1cb3..47fb10834223 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -174,17 +174,18 @@ static int dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 			 */
 			sk_error_report(sk);
 			dccp_done(sk);
-		} else
-			sk->sk_err_soft = err;
+		} else {
+			WRITE_ONCE(sk->sk_err_soft, err);
+		}
 		goto out;
 	}
 
 	if (!sock_owned_by_user(sk) && np->recverr) {
 		sk->sk_err = err;
 		sk_error_report(sk);
-	} else
-		sk->sk_err_soft = err;
-
+	} else {
+		WRITE_ONCE(sk->sk_err_soft, err);
+	}
 out:
 	bh_unlock_sock(sk);
 	sock_put(sk);
diff --git a/net/dccp/timer.c b/net/dccp/timer.c
index 27a3b37acd2e..b3255e87cc7e 100644
--- a/net/dccp/timer.c
+++ b/net/dccp/timer.c
@@ -19,7 +19,7 @@ int  sysctl_dccp_retries2		__read_mostly = TCP_RETR2;
 
 static void dccp_write_err(struct sock *sk)
 {
-	sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
+	sk->sk_err = READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT;
 	sk_error_report(sk);
 
 	dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED);
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 8db6747f892f..940062e08f57 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1322,7 +1322,7 @@ int inet_sk_rebuild_header(struct sock *sk)
 		    sk->sk_state != TCP_SYN_SENT ||
 		    (sk->sk_userlocks & SOCK_BINDADDR_LOCK) ||
 		    (err = inet_sk_reselect_saddr(sk)) != 0)
-			sk->sk_err_soft = -err;
+			WRITE_ONCE(sk->sk_err_soft, -err);
 	}
 
 	return err;
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 288693981b00..01569de651b6 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -589,7 +589,8 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
 	}
 	/* This barrier is coupled with smp_wmb() in tcp_reset() */
 	smp_rmb();
-	if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue))
+	if (READ_ONCE(sk->sk_err) ||
+	    !skb_queue_empty_lockless(&sk->sk_error_queue))
 		mask |= EPOLLERR;
 
 	return mask;
@@ -3094,7 +3095,7 @@ int tcp_disconnect(struct sock *sk, int flags)
 	if (old_state == TCP_LISTEN) {
 		inet_csk_listen_stop(sk);
 	} else if (unlikely(tp->repair)) {
-		sk->sk_err = ECONNABORTED;
+		WRITE_ONCE(sk->sk_err, ECONNABORTED);
 	} else if (tcp_need_reset(old_state) ||
 		   (tp->snd_nxt != tp->write_seq &&
 		    (1 << old_state) & (TCPF_CLOSING | TCPF_LAST_ACK))) {
@@ -3102,9 +3103,9 @@ int tcp_disconnect(struct sock *sk, int flags)
 		 * states
 		 */
 		tcp_send_active_reset(sk, gfp_any());
-		sk->sk_err = ECONNRESET;
+		WRITE_ONCE(sk->sk_err, ECONNRESET);
 	} else if (old_state == TCP_SYN_SENT)
-		sk->sk_err = ECONNRESET;
+		WRITE_ONCE(sk->sk_err, ECONNRESET);
 
 	tcp_clear_xmit_timers(sk);
 	__skb_queue_purge(&sk->sk_receive_queue);
@@ -4692,7 +4693,7 @@ int tcp_abort(struct sock *sk, int err)
 	bh_lock_sock(sk);
 
 	if (!sock_flag(sk, SOCK_DEAD)) {
-		sk->sk_err = err;
+		WRITE_ONCE(sk->sk_err, err);
 		/* This barrier is coupled with smp_rmb() in tcp_poll() */
 		smp_wmb();
 		sk_error_report(sk);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index cc072d2cfcd8..754ddbe0577f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3874,7 +3874,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	/* We passed data and got it acked, remove any soft error
 	 * log. Something worked...
 	 */
-	sk->sk_err_soft = 0;
+	WRITE_ONCE(sk->sk_err_soft, 0);
 	icsk->icsk_probes_out = 0;
 	tp->rcv_tstamp = tcp_jiffies32;
 	if (!prior_packets)
@@ -4322,15 +4322,15 @@ void tcp_reset(struct sock *sk, struct sk_buff *skb)
 	/* We want the right error as BSD sees it (and indeed as we do). */
 	switch (sk->sk_state) {
 	case TCP_SYN_SENT:
-		sk->sk_err = ECONNREFUSED;
+		WRITE_ONCE(sk->sk_err, ECONNREFUSED);
 		break;
 	case TCP_CLOSE_WAIT:
-		sk->sk_err = EPIPE;
+		WRITE_ONCE(sk->sk_err, EPIPE);
 		break;
 	case TCP_CLOSE:
 		return;
 	default:
-		sk->sk_err = ECONNRESET;
+		WRITE_ONCE(sk->sk_err, ECONNRESET);
 	}
 	/* This barrier is coupled with smp_rmb() in tcp_poll() */
 	smp_wmb();
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index ea370afa70ed..89daa6b953ff 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -361,7 +361,7 @@ void tcp_v4_mtu_reduced(struct sock *sk)
 	 * for the case, if this connection will not able to recover.
 	 */
 	if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
-		sk->sk_err_soft = EMSGSIZE;
+		WRITE_ONCE(sk->sk_err_soft, EMSGSIZE);
 
 	mtu = dst_mtu(dst);
 
@@ -596,13 +596,13 @@ int tcp_v4_err(struct sk_buff *skb, u32 info)
 		ip_icmp_error(sk, skb, err, th->dest, info, (u8 *)th);
 
 		if (!sock_owned_by_user(sk)) {
-			sk->sk_err = err;
+			WRITE_ONCE(sk->sk_err, err);
 
 			sk_error_report(sk);
 
 			tcp_done(sk);
 		} else {
-			sk->sk_err_soft = err;
+			WRITE_ONCE(sk->sk_err_soft, err);
 		}
 		goto out;
 	}
@@ -625,10 +625,10 @@ int tcp_v4_err(struct sk_buff *skb, u32 info)
 
 	inet = inet_sk(sk);
 	if (!sock_owned_by_user(sk) && inet->recverr) {
-		sk->sk_err = err;
+		WRITE_ONCE(sk->sk_err, err);
 		sk_error_report(sk);
 	} else	{ /* Only an error on timeout */
-		sk->sk_err_soft = err;
+		WRITE_ONCE(sk->sk_err_soft, err);
 	}
 
 out:
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 71d01cf3c13e..f7e00d90a730 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3699,7 +3699,7 @@ static void tcp_connect_init(struct sock *sk)
 	tp->rx_opt.rcv_wscale = rcv_wscale;
 	tp->rcv_ssthresh = tp->rcv_wnd;
 
-	sk->sk_err = 0;
+	WRITE_ONCE(sk->sk_err, 0);
 	sock_reset_flag(sk, SOCK_DONE);
 	tp->snd_wnd = 0;
 	tcp_init_wl(tp, 0);
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index cb79127f45c3..b839c2f91292 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -67,7 +67,7 @@ u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when)
 
 static void tcp_write_err(struct sock *sk)
 {
-	sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
+	WRITE_ONCE(sk->sk_err, READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT);
 	sk_error_report(sk);
 
 	tcp_write_queue_purge(sk);
@@ -110,7 +110,7 @@ static int tcp_out_of_resources(struct sock *sk, bool do_reset)
 		shift++;
 
 	/* If some dubious ICMP arrived, penalize even more. */
-	if (sk->sk_err_soft)
+	if (READ_ONCE(sk->sk_err_soft))
 		shift++;
 
 	if (tcp_check_oom(sk, shift)) {
@@ -146,7 +146,7 @@ static int tcp_orphan_retries(struct sock *sk, bool alive)
 	int retries = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_orphan_retries); /* May be zero. */
 
 	/* We know from an ICMP that something is wrong. */
-	if (sk->sk_err_soft && !alive)
+	if (READ_ONCE(sk->sk_err_soft) && !alive)
 		retries = 0;
 
 	/* However, if socket sent something recently, select some safe
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 38689bedfce7..e1b679a590c9 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -845,7 +845,7 @@ int inet6_sk_rebuild_header(struct sock *sk)
 		dst = ip6_dst_lookup_flow(sock_net(sk), sk, &fl6, final_p);
 		if (IS_ERR(dst)) {
 			sk->sk_route_caps = 0;
-			sk->sk_err_soft = -PTR_ERR(dst);
+			WRITE_ONCE(sk->sk_err_soft, -PTR_ERR(dst));
 			return PTR_ERR(dst);
 		}
 
diff --git a/net/ipv6/inet6_connection_sock.c b/net/ipv6/inet6_connection_sock.c
index 5a9f4d722f35..0c50dcd35fe8 100644
--- a/net/ipv6/inet6_connection_sock.c
+++ b/net/ipv6/inet6_connection_sock.c
@@ -120,7 +120,7 @@ int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl_unused
 
 	dst = inet6_csk_route_socket(sk, &fl6);
 	if (IS_ERR(dst)) {
-		sk->sk_err_soft = -PTR_ERR(dst);
+		WRITE_ONCE(sk->sk_err_soft, -PTR_ERR(dst));
 		sk->sk_route_caps = 0;
 		kfree_skb(skb);
 		return PTR_ERR(dst);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 1bf93b61aa06..35cf523c9efd 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -493,12 +493,13 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 		ipv6_icmp_error(sk, skb, err, th->dest, ntohl(info), (u8 *)th);
 
 		if (!sock_owned_by_user(sk)) {
-			sk->sk_err = err;
+			WRITE_ONCE(sk->sk_err, err);
 			sk_error_report(sk);		/* Wake people up to see the error (see connect in sock.c) */
 
 			tcp_done(sk);
-		} else
-			sk->sk_err_soft = err;
+		} else {
+			WRITE_ONCE(sk->sk_err_soft, err);
+		}
 		goto out;
 	case TCP_LISTEN:
 		break;
@@ -512,11 +513,11 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 	}
 
 	if (!sock_owned_by_user(sk) && np->recverr) {
-		sk->sk_err = err;
+		WRITE_ONCE(sk->sk_err, err);
 		sk_error_report(sk);
-	} else
-		sk->sk_err_soft = err;
-
+	} else {
+		WRITE_ONCE(sk->sk_err_soft, err);
+	}
 out:
 	bh_unlock_sock(sk);
 	sock_put(sk);
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 56628b52d100..cbaa1b49f7fe 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -2019,7 +2019,7 @@ static int mptcp_event_put_token_and_ssk(struct sk_buff *skb,
 	    nla_put_s32(skb, MPTCP_ATTR_IF_IDX, ssk->sk_bound_dev_if))
 		return -EMSGSIZE;
 
-	sk_err = ssk->sk_err;
+	sk_err = READ_ONCE(ssk->sk_err);
 	if (sk_err && sk->sk_state == TCP_ESTABLISHED &&
 	    nla_put_u8(skb, MPTCP_ATTR_ERROR, sk_err))
 		return -EMSGSIZE;
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 3ad9c46202fc..3005a5adf715 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2463,15 +2463,15 @@ static void mptcp_check_fastclose(struct mptcp_sock *msk)
 	/* Mirror the tcp_reset() error propagation */
 	switch (sk->sk_state) {
 	case TCP_SYN_SENT:
-		sk->sk_err = ECONNREFUSED;
+		WRITE_ONCE(sk->sk_err, ECONNREFUSED);
 		break;
 	case TCP_CLOSE_WAIT:
-		sk->sk_err = EPIPE;
+		WRITE_ONCE(sk->sk_err, EPIPE);
 		break;
 	case TCP_CLOSE:
 		return;
 	default:
-		sk->sk_err = ECONNRESET;
+		WRITE_ONCE(sk->sk_err, ECONNRESET);
 	}
 
 	inet_sk_state_store(sk, TCP_CLOSE);
@@ -3791,7 +3791,7 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock,
 
 	/* This barrier is coupled with smp_wmb() in __mptcp_error_report() */
 	smp_rmb();
-	if (sk->sk_err)
+	if (READ_ONCE(sk->sk_err))
 		mask |= EPOLLERR;
 
 	return mask;
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 4ae1a7304cf0..01874059a168 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1335,7 +1335,7 @@ fallback:
 			subflow->reset_reason = MPTCP_RST_EMPTCP;
 
 reset:
-			ssk->sk_err = EBADMSG;
+			WRITE_ONCE(ssk->sk_err, EBADMSG);
 			tcp_set_state(ssk, TCP_CLOSE);
 			while ((skb = skb_peek(&ssk->sk_receive_queue)))
 				sk_eat_skb(ssk, skb);
@@ -1419,7 +1419,7 @@ void __mptcp_error_report(struct sock *sk)
 		ssk_state = inet_sk_state_load(ssk);
 		if (ssk_state == TCP_CLOSE && !sock_flag(sk, SOCK_DEAD))
 			inet_sk_state_store(sk, ssk_state);
-		sk->sk_err = -err;
+		WRITE_ONCE(sk->sk_err, -err);
 
 		/* This barrier is coupled with smp_rmb() in mptcp_poll() */
 		smp_wmb();
diff --git a/net/sctp/input.c b/net/sctp/input.c
index bf70371301ff..127bf28a6033 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -585,7 +585,7 @@ static void sctp_v4_err_handle(struct sctp_transport *t, struct sk_buff *skb,
 		sk->sk_err = err;
 		sk_error_report(sk);
 	} else {  /* Only an error on timeout */
-		sk->sk_err_soft = err;
+		WRITE_ONCE(sk->sk_err_soft, err);
 	}
 }
 
diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
index 62b436a2c8fe..43f2731bf590 100644
--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -155,7 +155,7 @@ static void sctp_v6_err_handle(struct sctp_transport *t, struct sk_buff *skb,
 		sk->sk_err = err;
 		sk_error_report(sk);
 	} else {
-		sk->sk_err_soft = err;
+		WRITE_ONCE(sk->sk_err_soft, err);
 	}
 }
 
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 0b0f18ecce44..fb31e8a4409e 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -557,7 +557,7 @@ static void unix_dgram_disconnected(struct sock *sk, struct sock *other)
 		 * when peer was not connected to us.
 		 */
 		if (!sock_flag(other, SOCK_DEAD) && unix_peer(other) == sk) {
-			other->sk_err = ECONNRESET;
+			WRITE_ONCE(other->sk_err, ECONNRESET);
 			sk_error_report(other);
 		}
 	}
@@ -630,7 +630,7 @@ static void unix_release_sock(struct sock *sk, int embrion)
 			/* No more writes */
 			skpair->sk_shutdown = SHUTDOWN_MASK;
 			if (!skb_queue_empty(&sk->sk_receive_queue) || embrion)
-				skpair->sk_err = ECONNRESET;
+				WRITE_ONCE(skpair->sk_err, ECONNRESET);
 			unix_state_unlock(skpair);
 			skpair->sk_state_change(skpair);
 			sk_wake_async(skpair, SOCK_WAKE_WAITD, POLL_HUP);
@@ -3165,7 +3165,7 @@ static __poll_t unix_poll(struct file *file, struct socket *sock, poll_table *wa
 	mask = 0;
 
 	/* exceptional events? */
-	if (sk->sk_err)
+	if (READ_ONCE(sk->sk_err))
 		mask |= EPOLLERR;
 	if (sk->sk_shutdown == SHUTDOWN_MASK)
 		mask |= EPOLLHUP;
@@ -3208,7 +3208,8 @@ static __poll_t unix_dgram_poll(struct file *file, struct socket *sock,
 	mask = 0;
 
 	/* exceptional events? */
-	if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue))
+	if (READ_ONCE(sk->sk_err) ||
+	    !skb_queue_empty_lockless(&sk->sk_error_queue))
 		mask |= EPOLLERR |
 			(sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? EPOLLPRI : 0);