From: Eric Dumazet <edumazet@google.com>
Date: Mon, 30 Jun 2025 12:19:27 +0000 (+0000)
Subject: net: dst: annotate data-races around dst->lastuse
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8f2b2282d04a5d5bcbec22f91572bb6803cfc771;p=thirdparty%2Flinux.git

net: dst: annotate data-races around dst->lastuse

(dst_entry)->lastuse is read and written locklessly,
add corresponding annotations.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250630121934.3399505-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/include/net/dst.h b/include/net/dst.h
index 1efe1e5d51a90..bef2f41c72204 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -240,9 +240,9 @@ static inline void dst_hold(struct dst_entry *dst)
 
 static inline void dst_use_noref(struct dst_entry *dst, unsigned long time)
 {
-	if (unlikely(time != dst->lastuse)) {
+	if (unlikely(time != READ_ONCE(dst->lastuse))) {
 		dst->__use++;
-		dst->lastuse = time;
+		WRITE_ONCE(dst->lastuse, time);
 	}
 }
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index c57692eb8da9d..a9555bfc372f5 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1026,9 +1026,11 @@ int rtnl_put_cacheinfo(struct sk_buff *skb, struct dst_entry *dst, u32 id,
 		.rta_error = error,
 		.rta_id =  id,
 	};
+	unsigned long delta;
 
 	if (dst) {
-		ci.rta_lastuse = jiffies_delta_to_clock_t(jiffies - dst->lastuse);
+		delta = jiffies - READ_ONCE(dst->lastuse);
+		ci.rta_lastuse = jiffies_delta_to_clock_t(delta);
 		ci.rta_used = dst->__use;
 		ci.rta_clntref = rcuref_read(&dst->__rcuref);
 	}
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 1014dcea1200c..375112a59492e 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2133,7 +2133,8 @@ static void rt6_age_examine_exception(struct rt6_exception_bucket *bucket,
 	 * expired, independently from their aging, as per RFC 8201 section 4
 	 */
 	if (!(rt->rt6i_flags & RTF_EXPIRES)) {
-		if (time_after_eq(now, rt->dst.lastuse + gc_args->timeout)) {
+		if (time_after_eq(now, READ_ONCE(rt->dst.lastuse) +
+				       gc_args->timeout)) {
 			pr_debug("aging clone %p\n", rt);
 			rt6_remove_exception(bucket, rt6_ex);
 			return;