netdev - [PATCH net 05/11] net: annotate data-races around sk->sk

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Message-ID: <20230728150318.2055273-6-edumazet@google.com>
Date: Fri, 28 Jul 2023 15:03:12 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang <xiyou.wangcong@...il.com>, 
	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net 05/11] net: annotate data-races around sk->sk_{rcv|snd}timeo

sk_getsockopt() runs without locks, we must add annotations
to sk->sk_rcvtimeo and sk->sk_sndtimeo.

In the future we might allow fetching these fields before
we lock the socket in TCP fast path.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/sock.c     | 24 ++++++++++++++----------
 net/sched/em_meta.c |  4 ++--
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 08e60500160571e46c798e6cd71d56234a516fd3..264c99c190ac9a550d93b760d78f006b216fcb75 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -429,6 +429,7 @@ static int sock_set_timeout(long *timeo_p, sockptr_t optval, int optlen,
 {
 	struct __kernel_sock_timeval tv;
 	int err = sock_copy_user_timeval(&tv, optval, optlen, old_timeval);
+	long val;
 
 	if (err)
 		return err;
@@ -439,7 +440,7 @@ static int sock_set_timeout(long *timeo_p, sockptr_t optval, int optlen,
 	if (tv.tv_sec < 0) {
 		static int warned __read_mostly;
 
-		*timeo_p = 0;
+		WRITE_ONCE(*timeo_p, 0);
 		if (warned < 10 && net_ratelimit()) {
 			warned++;
 			pr_info("%s: `%s' (pid %d) tries to set negative timeout\n",
@@ -447,11 +448,12 @@ static int sock_set_timeout(long *timeo_p, sockptr_t optval, int optlen,
 		}
 		return 0;
 	}
-	*timeo_p = MAX_SCHEDULE_TIMEOUT;
-	if (tv.tv_sec == 0 && tv.tv_usec == 0)
-		return 0;
-	if (tv.tv_sec < (MAX_SCHEDULE_TIMEOUT / HZ - 1))
-		*timeo_p = tv.tv_sec * HZ + DIV_ROUND_UP((unsigned long)tv.tv_usec, USEC_PER_SEC / HZ);
+	val = MAX_SCHEDULE_TIMEOUT;
+	if ((tv.tv_sec || tv.tv_usec) &&
+	    (tv.tv_sec < (MAX_SCHEDULE_TIMEOUT / HZ - 1)))
+		val = tv.tv_sec * HZ + DIV_ROUND_UP((unsigned long)tv.tv_usec,
+						    USEC_PER_SEC / HZ);
+	WRITE_ONCE(*timeo_p, val);
 	return 0;
 }
 
@@ -813,9 +815,9 @@ void sock_set_sndtimeo(struct sock *sk, s64 secs)
 {
 	lock_sock(sk);
 	if (secs && secs < MAX_SCHEDULE_TIMEOUT / HZ - 1)
-		sk->sk_sndtimeo = secs * HZ;
+		WRITE_ONCE(sk->sk_sndtimeo, secs * HZ);
 	else
-		sk->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
+		WRITE_ONCE(sk->sk_sndtimeo, MAX_SCHEDULE_TIMEOUT);
 	release_sock(sk);
 }
 EXPORT_SYMBOL(sock_set_sndtimeo);
@@ -1721,12 +1723,14 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
 
 	case SO_RCVTIMEO_OLD:
 	case SO_RCVTIMEO_NEW:
-		lv = sock_get_timeout(sk->sk_rcvtimeo, &v, SO_RCVTIMEO_OLD == optname);
+		lv = sock_get_timeout(READ_ONCE(sk->sk_rcvtimeo), &v,
+				      SO_RCVTIMEO_OLD == optname);
 		break;
 
 	case SO_SNDTIMEO_OLD:
 	case SO_SNDTIMEO_NEW:
-		lv = sock_get_timeout(sk->sk_sndtimeo, &v, SO_SNDTIMEO_OLD == optname);
+		lv = sock_get_timeout(READ_ONCE(sk->sk_sndtimeo), &v,
+				      SO_SNDTIMEO_OLD == optname);
 		break;
 
 	case SO_RCVLOWAT:
diff --git a/net/sched/em_meta.c b/net/sched/em_meta.c
index af85a73c4c5458ec9b018e5f43f420a3b2079917..6fdba069f6bfd306fa68fc2e68bdcaf0cf4d4e9e 100644
--- a/net/sched/em_meta.c
+++ b/net/sched/em_meta.c
@@ -568,7 +568,7 @@ META_COLLECTOR(int_sk_rcvtimeo)
 		*err = -1;
 		return;
 	}
-	dst->value = sk->sk_rcvtimeo / HZ;
+	dst->value = READ_ONCE(sk->sk_rcvtimeo) / HZ;
 }
 
 META_COLLECTOR(int_sk_sndtimeo)
@@ -579,7 +579,7 @@ META_COLLECTOR(int_sk_sndtimeo)
 		*err = -1;
 		return;
 	}
-	dst->value = sk->sk_sndtimeo / HZ;
+	dst->value = READ_ONCE(sk->sk_sndtimeo) / HZ;
 }
 
 META_COLLECTOR(int_sk_sendmsg_off)
-- 
2.41.0.585.gd2178a4bd4-goog