[PATCH net-next v2 4/9] net: bridge: vlan: annotate lockless vlan flags use

[Nikolay Aleksandrov <razor@blackwall.org>]

Annotate vlan flags data races, they can be read lockless.

Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>
---
 net/bridge/br_multicast.c |  2 +-
 net/bridge/br_netlink.c   |  6 +++---
 net/bridge/br_private.h   |  4 ++--
 net/bridge/br_vlan.c      | 19 +++++++++++--------
 4 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 3ef5d8bbf552..bbcaedf15ca1 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -912,7 +912,7 @@ static void __br_multicast_query_handle_vlan(struct net_bridge_mcast *brmctx,
 	else if (br_multicast_ctx_is_vlan(brmctx))
 		vlan = brmctx->vlan;
 
-	if (vlan && !(vlan->flags & BRIDGE_VLAN_INFO_UNTAGGED)) {
+	if (vlan && !(READ_ONCE(vlan->flags) & BRIDGE_VLAN_INFO_UNTAGGED)) {
 		u16 vlan_proto;
 
 		if (br_vlan_get_proto(brmctx->br->dev, &vlan_proto) != 0)
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index b2cd4e39326d..62ce96d9ba32 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -41,7 +41,7 @@ static int __get_num_vlan_infos(struct net_bridge_vlan_group *vg,
 		if (v->vid == pvid)
 			flags |= BRIDGE_VLAN_INFO_PVID;
 
-		if (v->flags & BRIDGE_VLAN_INFO_UNTAGGED)
+		if (READ_ONCE(v->flags) & BRIDGE_VLAN_INFO_UNTAGGED)
 			flags |= BRIDGE_VLAN_INFO_UNTAGGED;
 
 		if (vid_range_start == 0) {
@@ -385,7 +385,7 @@ static int br_fill_ifvlaninfo_compressed(struct sk_buff *skb,
 		if (v->vid == pvid)
 			flags |= BRIDGE_VLAN_INFO_PVID;
 
-		if (v->flags & BRIDGE_VLAN_INFO_UNTAGGED)
+		if (READ_ONCE(v->flags) & BRIDGE_VLAN_INFO_UNTAGGED)
 			flags |= BRIDGE_VLAN_INFO_UNTAGGED;
 
 		if (vid_range_start == 0) {
@@ -437,7 +437,7 @@ static int br_fill_ifvlaninfo(struct sk_buff *skb,
 		if (v->vid == pvid)
 			vinfo.flags |= BRIDGE_VLAN_INFO_PVID;
 
-		if (v->flags & BRIDGE_VLAN_INFO_UNTAGGED)
+		if (READ_ONCE(v->flags) & BRIDGE_VLAN_INFO_UNTAGGED)
 			vinfo.flags |= BRIDGE_VLAN_INFO_UNTAGGED;
 
 		if (nla_put(skb, IFLA_BRIDGE_VLAN_INFO,
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 0efd2e79e255..96554d293d22 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -665,13 +665,13 @@ static inline int br_is_root_bridge(const struct net_bridge *br)
 /* check if a VLAN entry is global */
 static inline bool br_vlan_is_master(const struct net_bridge_vlan *v)
 {
-	return v->flags & BRIDGE_VLAN_INFO_MASTER;
+	return READ_ONCE(v->flags) & BRIDGE_VLAN_INFO_MASTER;
 }
 
 /* check if a VLAN entry is used by the bridge */
 static inline bool br_vlan_is_brentry(const struct net_bridge_vlan *v)
 {
-	return v->flags & BRIDGE_VLAN_INFO_BRENTRY;
+	return READ_ONCE(v->flags) & BRIDGE_VLAN_INFO_BRENTRY;
 }
 
 /* check if we should use the vlan entry, returns false if it's only context */
diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index a53054fcc093..c8b2e3bfd42d 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -60,6 +60,7 @@ static bool __vlan_flags_update(struct net_bridge_vlan *v, u16 flags,
 				bool commit)
 {
 	struct net_bridge_vlan_group *vg;
+	u16 vlan_flags;
 	bool change;
 
 	if (br_vlan_is_master(v))
@@ -68,8 +69,9 @@ static bool __vlan_flags_update(struct net_bridge_vlan *v, u16 flags,
 		vg = nbp_vlan_group(v->port);
 
 	/* check if anything would be changed on commit */
+	vlan_flags = v->flags;
 	change = !!(flags & BRIDGE_VLAN_INFO_PVID) == !!(vg->pvid != v->vid) ||
-		 ((flags ^ v->flags) & BRIDGE_VLAN_INFO_UNTAGGED);
+		 ((flags ^ vlan_flags) & BRIDGE_VLAN_INFO_UNTAGGED);
 
 	if (!commit)
 		goto out;
@@ -80,9 +82,10 @@ static bool __vlan_flags_update(struct net_bridge_vlan *v, u16 flags,
 		__vlan_delete_pvid(vg, v->vid);
 
 	if (flags & BRIDGE_VLAN_INFO_UNTAGGED)
-		v->flags |= BRIDGE_VLAN_INFO_UNTAGGED;
+		vlan_flags |= BRIDGE_VLAN_INFO_UNTAGGED;
 	else
-		v->flags &= ~BRIDGE_VLAN_INFO_UNTAGGED;
+		vlan_flags &= ~BRIDGE_VLAN_INFO_UNTAGGED;
+	WRITE_ONCE(v->flags, vlan_flags);
 
 out:
 	return change;
@@ -413,7 +416,7 @@ static int __vlan_del(struct net_bridge_vlan *v)
 	}
 
 	if (br_vlan_should_use(v)) {
-		v->flags &= ~BRIDGE_VLAN_INFO_BRENTRY;
+		WRITE_ONCE(v->flags, v->flags & ~BRIDGE_VLAN_INFO_BRENTRY);
 		vg->num_vlans--;
 	}
 
@@ -522,7 +525,7 @@ struct sk_buff *br_handle_vlan(struct net_bridge *br,
 	 * hardware on each egress port as appropriate. So only strip the VLAN
 	 * header if forwarding offload is not being used.
 	 */
-	if (v->flags & BRIDGE_VLAN_INFO_UNTAGGED &&
+	if (READ_ONCE(v->flags) & BRIDGE_VLAN_INFO_UNTAGGED &&
 	    !br_switchdev_frame_uses_tx_fwd_offload(skb))
 		__vlan_hwaccel_clear_tag(skb);
 
@@ -753,7 +756,7 @@ static int br_vlan_add_existing(struct net_bridge *br,
 		}
 
 		refcount_inc(&vlan->refcnt);
-		vlan->flags |= BRIDGE_VLAN_INFO_BRENTRY;
+		WRITE_ONCE(vlan->flags, vlan->flags | BRIDGE_VLAN_INFO_BRENTRY);
 		vg->num_vlans++;
 		*changed = true;
 		br_multicast_toggle_one_vlan(vlan, true);
@@ -1489,7 +1492,7 @@ int br_vlan_fill_forward_path_mode(struct net_bridge *br,
 	if (!v || !br_vlan_should_use(v))
 		return -EINVAL;
 
-	if (!(v->flags & BRIDGE_VLAN_INFO_UNTAGGED))
+	if (!(READ_ONCE(v->flags) & BRIDGE_VLAN_INFO_UNTAGGED))
 		return 0;
 
 	if (path->bridge.vlan_mode == DEV_PATH_BR_VLAN_TAG)
@@ -1550,7 +1553,7 @@ int br_vlan_get_info_rcu(const struct net_device *dev, u16 vid,
 		return -ENOENT;
 
 	p_vinfo->vid = vid;
-	p_vinfo->flags = v->flags;
+	p_vinfo->flags = READ_ONCE(v->flags);
 	if (vid == br_get_pvid(vg))
 		p_vinfo->flags |= BRIDGE_VLAN_INFO_PVID;
 	return 0;
-- 
2.47.3