netdev - [PATCH net-next 2/6] dccp: annotate lockless accesses to sk->sk_err

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Date:   Wed, 15 Mar 2023 20:57:42 +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:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 2/6] dccp: annotate lockless accesses to sk->sk_err_soft

This field can be read/written without lock synchronization.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/dccp/ipv4.c  | 12 +++++++-----
 net/dccp/ipv6.c  | 11 ++++++-----
 net/dccp/timer.c |  2 +-
 3 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index b780827f5e0a5b4296e1e6a2e78dbd7f111d3402..3ab68415d121ce393168030b6821215ff28b1af4 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 b9d7c3dd1cb39852be3a03556e976c09757d391d..47fb108342239a0d26de913021ed489216bf5093 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 27a3b37acd2efea080d1d52e9f4097046e61f05f..b3255e87cc7e130bbcbfd1cd4aa98ba03d7cefaf 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);
-- 
2.40.0.rc2.332.ga46443480c-goog