[PATCH net v1] raw: annotate disconnect-side IPv4 match writers

[Xuanqiang Luo <xuanqiang.luo@linux.dev>]

From: Xuanqiang Luo <luoxuanqiang@kylinos.cn>

raw_v4_match() reads inet_daddr, inet_rcv_saddr and
sk_bound_dev_if locklessly under RCU. Bind and connect writers are
annotated, but __udp_disconnect() still clears the same fields using
plain stores.

Commit 18f116931f52e ("raw: annotate lockless match fields in
raw_v4_match()") added the lockless readers and annotated the raw bind
and datagram connect writers. Its v4 revision intentionally left the
shared disconnect-side IPv4 writers for follow-up cleanup.

Complete that follow-up by using WRITE_ONCE() for the disconnect-side
stores, including the inet_rcv_saddr reset in inet_reset_saddr(), to
pair with the lockless raw socket matcher.

Fixes: 0daf07e52709 ("raw: convert raw sockets to RCU")
Link: https://lore.kernel.org/netdev/20260716142958.3064224-1-runyu.xiao@seu.edu.cn/
Suggested-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
---
 include/net/ip.h | 3 ++-
 net/ipv4/udp.c   | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index a8f57b4f4aa23..6f602df72ee62 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -704,7 +704,8 @@ static inline void ip_ipgre_mc_map(__be32 naddr, const unsigned char *broadcast,
 
 static __inline__ void inet_reset_saddr(struct sock *sk)
 {
-	inet_sk(sk)->inet_rcv_saddr = inet_sk(sk)->inet_saddr = 0;
+	inet_sk(sk)->inet_saddr = 0;
+	WRITE_ONCE(inet_sk(sk)->inet_rcv_saddr, 0);
 #if IS_ENABLED(CONFIG_IPV6)
 	if (sk->sk_family == PF_INET6) {
 		struct ipv6_pinfo *np = inet6_sk(sk);
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index af96032174441..6ff5670bf6ed1 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2166,10 +2166,10 @@ int __udp_disconnect(struct sock *sk, int flags)
 	 */
 
 	sk->sk_state = TCP_CLOSE;
-	inet->inet_daddr = 0;
+	WRITE_ONCE(inet->inet_daddr, 0);
 	inet->inet_dport = 0;
 	sock_rps_reset_rxhash(sk);
-	sk->sk_bound_dev_if = 0;
+	WRITE_ONCE(sk->sk_bound_dev_if, 0);
 	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK)) {
 		inet_reset_saddr(sk);
 		if (sk->sk_prot->rehash &&
-- 
2.43.0