From: Vladimir Oltean <vladimir.oltean@xxxxxxx>
Annotate the writer side of fdb->dst:
- fdb_create()
- br_fdb_update()
- fdb_add_entry()
- br_fdb_external_learn_add()
with WRITE_ONCE() and the reader side:
- br_fdb_test_addr()
- br_fdb_update()
- fdb_fill_info()
- fdb_add_entry()
- fdb_delete_by_addr_and_port()
- br_fdb_external_learn_add()
- br_switchdev_fdb_notify()
with compiler barriers such that the readers do not attempt to reload
fdb->dst multiple times, leading to potentially different destination
ports when the fdb entry is updated concurrently.
This is especially important in read-side sections where fdb->dst is
used more than once, but let's convert all accesses for the sake of
uniformity.
Suggested-by: Nikolay Aleksandrov <nikolay@xxxxxxxxxx>
Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
---
v4->v5: patch is new
net/bridge/br_fdb.c | 28 +++++++++++++++++-----------
net/bridge/br_switchdev.c | 7 ++++---
2 files changed, 21 insertions(+), 14 deletions(-)
diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 16f9434fdb5d..dc3ecf2d5637 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -440,9 +440,14 @@ int br_fdb_test_addr(struct net_device *dev, unsigned char *addr)
if (!port)
ret = 0;
else {
+ const struct net_bridge_port *dst = NULL;
+
fdb = br_fdb_find_rcu(port->br, addr, 0);
- ret = fdb && fdb->dst && fdb->dst->dev != dev &&
- fdb->dst->state == BR_STATE_FORWARDING;
+ if (fdb)
+ dst = READ_ONCE(fdb->dst);
+
+ ret = dst && dst->dev != dev &&
+ dst->state == BR_STATE_FORWARDING;
}
rcu_read_unlock();
@@ -509,7 +514,7 @@ static struct net_bridge_fdb_entry *fdb_create(struct net_bridge *br,
fdb = kmem_cache_alloc(br_fdb_cache, GFP_ATOMIC);
if (fdb) {
memcpy(fdb->key.addr.addr, addr, ETH_ALEN);
- fdb->dst = source;
+ WRITE_ONCE(fdb->dst, source);
fdb->key.vlan_id = vid;
fdb->flags = flags;
fdb->updated = fdb->used = jiffies;
@@ -600,10 +605,10 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
}
/* fastpath: update of existing entry */
- if (unlikely(source != fdb->dst &&
+ if (unlikely(source != READ_ONCE(fdb->dst) &&
!test_bit(BR_FDB_STICKY, &fdb->flags))) {
br_switchdev_fdb_notify(fdb, RTM_DELNEIGH);
- fdb->dst = source;
+ WRITE_ONCE(fdb->dst, source);
fdb_modified = true;
/* Take over HW learned entry */
if (unlikely(test_bit(BR_FDB_ADDED_BY_EXT_LEARN,
@@ -650,6 +655,7 @@ static int fdb_fill_info(struct sk_buff *skb, const struct net_bridge *br,
const struct net_bridge_fdb_entry *fdb,
u32 portid, u32 seq, int type, unsigned int flags)
{
+ const struct net_bridge_port *dst = READ_ONCE(fdb->dst);
unsigned long now = jiffies;
struct nda_cacheinfo ci;
struct nlmsghdr *nlh;
@@ -665,7 +671,7 @@ static int fdb_fill_info(struct sk_buff *skb, const struct net_bridge *br,
ndm->ndm_pad2 = 0;
ndm->ndm_flags = 0;
ndm->ndm_type = 0;
- ndm->ndm_ifindex = fdb->dst ? fdb->dst->dev->ifindex : br->dev->ifindex;
+ ndm->ndm_ifindex = dst ? dst->dev->ifindex : br->dev->ifindex;
ndm->ndm_state = fdb_to_nud(br, fdb);
if (test_bit(BR_FDB_OFFLOADED, &fdb->flags))
@@ -964,8 +970,8 @@ static int fdb_add_entry(struct net_bridge *br, struct net_bridge_port *source,
if (flags & NLM_F_EXCL)
return -EEXIST;
- if (fdb->dst != source) {
- fdb->dst = source;
+ if (READ_ONCE(fdb->dst) != source) {
+ WRITE_ONCE(fdb->dst, source);
modified = true;
}
}
@@ -1132,7 +1138,7 @@ static int fdb_delete_by_addr_and_port(struct net_bridge *br,
struct net_bridge_fdb_entry *fdb;
fdb = br_fdb_find(br, addr, vlan);
- if (!fdb || fdb->dst != p)
+ if (!fdb || READ_ONCE(fdb->dst) != p)
return -ENOENT;
fdb_delete(br, fdb, true);
@@ -1281,8 +1287,8 @@ int br_fdb_external_learn_add(struct net_bridge *br, struct net_bridge_port *p,
} else {
fdb->updated = jiffies;
- if (fdb->dst != p) {
- fdb->dst = p;
+ if (READ_ONCE(fdb->dst) != p) {
+ WRITE_ONCE(fdb->dst, p);
modified = true;
}
diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c
index a5e601e41cb9..192293fe37fd 100644
--- a/net/bridge/br_switchdev.c
+++ b/net/bridge/br_switchdev.c
@@ -110,6 +110,7 @@ int br_switchdev_set_port_flag(struct net_bridge_port *p,
void
br_switchdev_fdb_notify(const struct net_bridge_fdb_entry *fdb, int type)
{
+ const struct net_bridge_port *dst = READ_ONCE(fdb->dst);
struct switchdev_notifier_fdb_info info = {
.addr = fdb->key.addr.addr,
.vid = fdb->key.vlan_id,
@@ -118,17 +119,17 @@ br_switchdev_fdb_notify(const struct net_bridge_fdb_entry *fdb, int type)
.offloaded = test_bit(BR_FDB_OFFLOADED, &fdb->flags),
};
- if (!fdb->dst)
+ if (!dst)
return;
switch (type) {
case RTM_DELNEIGH:
call_switchdev_notifiers(SWITCHDEV_FDB_DEL_TO_DEVICE,
- fdb->dst->dev, &info.info, NULL);
+ dst->dev, &info.info, NULL);
break;
case RTM_NEWNEIGH:
call_switchdev_notifiers(SWITCHDEV_FDB_ADD_TO_DEVICE,
- fdb->dst->dev, &info.info, NULL);
+ dst->dev, &info.info, NULL);
break;
}
}
--
2.25.1
