Merge branch 'u64_stats-introduce-u64_stats_copy'

David Yang says:

====================
u64_stats: Introduce u64_stats_copy()

On 64bit arches, struct u64_stats_sync is empty and provides no help
against load/store tearing. memcpy() should not be considered atomic
against u64 values. Use u64_stats_copy() instead.
====================

Link: https://patch.msgid.link/20260120092137.2161162-1-mmyangfl@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

4 files changed, 20 insertions, 5 deletions

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index 5200fd5a10e5..c2cb2d20976b 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -2806,7 +2806,7 @@ static void get_rx_sc_stats(struct net_device *dev,
 		stats = per_cpu_ptr(rx_sc->stats, cpu);
 		do {
 			start = u64_stats_fetch_begin(&stats->syncp);
-			memcpy(&tmp, &stats->stats, sizeof(tmp));
+			u64_stats_copy(&tmp, &stats->stats, sizeof(tmp));
 		} while (u64_stats_fetch_retry(&stats->syncp, start));
 
 		sum->InOctetsValidated += tmp.InOctetsValidated;
@@ -2887,7 +2887,7 @@ static void get_tx_sc_stats(struct net_device *dev,
 		stats = per_cpu_ptr(macsec_priv(dev)->secy.tx_sc.stats, cpu);
 		do {
 			start = u64_stats_fetch_begin(&stats->syncp);
-			memcpy(&tmp, &stats->stats, sizeof(tmp));
+			u64_stats_copy(&tmp, &stats->stats, sizeof(tmp));
 		} while (u64_stats_fetch_retry(&stats->syncp, start));
 
 		sum->OutPktsProtected   += tmp.OutPktsProtected;
@@ -2943,7 +2943,7 @@ static void get_secy_stats(struct net_device *dev, struct macsec_dev_stats *sum)
 		stats = per_cpu_ptr(macsec_priv(dev)->stats, cpu);
 		do {
 			start = u64_stats_fetch_begin(&stats->syncp);
-			memcpy(&tmp, &stats->stats, sizeof(tmp));
+			u64_stats_copy(&tmp, &stats->stats, sizeof(tmp));
 		} while (u64_stats_fetch_retry(&stats->syncp, start));
 
 		sum->OutPktsUntagged  += tmp.OutPktsUntagged;
diff --git a/drivers/net/vxlan/vxlan_vnifilter.c b/drivers/net/vxlan/vxlan_vnifilter.c
index adc89e651e27..cde897d92f24 100644
--- a/drivers/net/vxlan/vxlan_vnifilter.c
+++ b/drivers/net/vxlan/vxlan_vnifilter.c
@@ -126,7 +126,7 @@ static void vxlan_vnifilter_stats_get(const struct vxlan_vni_node *vninode,
 		pstats = per_cpu_ptr(vninode->stats, i);
 		do {
 			start = u64_stats_fetch_begin(&pstats->syncp);
-			memcpy(&temp, &pstats->stats, sizeof(temp));
+			u64_stats_copy(&temp, &pstats->stats, sizeof(temp));
 		} while (u64_stats_fetch_retry(&pstats->syncp, start));
 
 		dest->rx_packets += temp.rx_packets;
diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
index 457879938fc1..849ff6e159c6 100644
--- a/include/linux/u64_stats_sync.h
+++ b/include/linux/u64_stats_sync.h
@@ -79,6 +79,14 @@ static inline u64 u64_stats_read(const u64_stats_t *p)
 	return local64_read(&p->v);
 }
 
+static inline void *u64_stats_copy(void *dst, const void *src, size_t len)
+{
+	BUILD_BUG_ON(len % sizeof(u64_stats_t));
+	for (size_t i = 0; i < len / sizeof(u64_stats_t); i++)
+		((u64 *)dst)[i] = local64_read(&((local64_t *)src)[i]);
+	return dst;
+}
+
 static inline void u64_stats_set(u64_stats_t *p, u64 val)
 {
 	local64_set(&p->v, val);
@@ -110,6 +118,7 @@ static inline bool __u64_stats_fetch_retry(const struct u64_stats_sync *syncp,
 }
 
 #else /* 64 bit */
+#include <linux/string.h>
 
 typedef struct {
 	u64		v;
@@ -120,6 +129,12 @@ static inline u64 u64_stats_read(const u64_stats_t *p)
 	return p->v;
 }
 
+static inline void *u64_stats_copy(void *dst, const void *src, size_t len)
+{
+	BUILD_BUG_ON(len % sizeof(u64_stats_t));
+	return memcpy(dst, src, len);
+}
+
 static inline void u64_stats_set(u64_stats_t *p, u64 val)
 {
 	p->v = val;
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index d55a4ab87837..dccae08b4f4c 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -5201,7 +5201,7 @@ void br_multicast_get_stats(const struct net_bridge *br,
 
 		do {
 			start = u64_stats_fetch_begin(&cpu_stats->syncp);
-			memcpy(&temp, &cpu_stats->mstats, sizeof(temp));
+			u64_stats_copy(&temp, &cpu_stats->mstats, sizeof(temp));
 		} while (u64_stats_fetch_retry(&cpu_stats->syncp, start));
 
 		mcast_stats_add_dir(tdst.igmp_v1queries, temp.igmp_v1queries);