* [PATCH net-next 1/2] macvlan: annotate data-races around vlan->mode and vlan->flags
2026-07-01 8:22 [PATCH net-next 0/2] macvlan: RTNL-less macvlan_fill_info() Eric Dumazet
@ 2026-07-01 8:22 ` Eric Dumazet
2026-07-01 12:09 ` Nikolay Aleksandrov
2026-07-01 8:22 ` [PATCH net-next 2/2] macvlan: no longer rely on RTNL in macvlan_fill_info() Eric Dumazet
1 sibling, 1 reply; 5+ messages in thread
From: Eric Dumazet @ 2026-07-01 8:22 UTC (permalink / raw)
To: David S . Miller, Jakub Kicinski, Paolo Abeni
Cc: Simon Horman, Kuniyuki Iwashima, netdev, eric.dumazet,
Eric Dumazet
Both fields can be changed in macvlan_changelink() while being read
locklessly.
Add READ_ONCE()/WRITE_ONCE() annotations.
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
drivers/net/macvlan.c | 38 +++++++++++++++++++++-----------------
1 file changed, 21 insertions(+), 17 deletions(-)
diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index c40fa331836bb2395267914807542ae5094e1a3c..8b69cc9b70f98d7991110f5eda76d58d5d96fa81 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -277,7 +277,7 @@ static void macvlan_broadcast(struct sk_buff *skb,
return;
hash_for_each_rcu(port->vlan_hash, i, vlan, hlist) {
- if (vlan->dev == src || !(vlan->mode & mode))
+ if (vlan->dev == src || !(READ_ONCE(vlan->mode) & mode))
continue;
hash = mc_hash(vlan, eth->h_dest);
@@ -306,7 +306,7 @@ static void macvlan_multicast_rx(const struct macvlan_port *port,
MACVLAN_MODE_VEPA |
MACVLAN_MODE_PASSTHRU|
MACVLAN_MODE_BRIDGE);
- else if (src->mode == MACVLAN_MODE_VEPA)
+ else if (READ_ONCE(src->mode) == MACVLAN_MODE_VEPA)
/* flood to everyone except source */
macvlan_broadcast(skb, port, src->dev,
MACVLAN_MODE_VEPA |
@@ -447,7 +447,7 @@ static bool macvlan_forward_source(struct sk_buff *skb,
if (!vlan)
continue;
- if (vlan->flags & MACVLAN_FLAG_NODST)
+ if (READ_ONCE(vlan->flags) & MACVLAN_FLAG_NODST)
consume = true;
macvlan_forward_source_one(skb, vlan);
}
@@ -487,14 +487,18 @@ static rx_handler_result_t macvlan_handle_frame(struct sk_buff **pskb)
return RX_HANDLER_CONSUMED;
}
src = macvlan_hash_lookup(port, eth->h_source);
- if (src && src->mode != MACVLAN_MODE_VEPA &&
- src->mode != MACVLAN_MODE_BRIDGE) {
- /* forward to original port. */
- vlan = src;
- ret = macvlan_broadcast_one(skb, vlan, eth, 0) ?:
- __netif_rx(skb);
- handle_res = RX_HANDLER_CONSUMED;
- goto out;
+ if (src) {
+ enum macvlan_mode mode = READ_ONCE(src->mode);
+
+ if (mode != MACVLAN_MODE_VEPA &&
+ mode != MACVLAN_MODE_BRIDGE) {
+ /* forward to original port. */
+ vlan = src;
+ ret = macvlan_broadcast_one(skb, vlan, eth, 0) ?:
+ __netif_rx(skb);
+ handle_res = RX_HANDLER_CONSUMED;
+ goto out;
+ }
}
hash = mc_hash(NULL, eth->h_dest);
@@ -515,7 +519,7 @@ static rx_handler_result_t macvlan_handle_frame(struct sk_buff **pskb)
struct macvlan_dev, list);
else
vlan = macvlan_hash_lookup(port, eth->h_dest);
- if (!vlan || vlan->mode == MACVLAN_MODE_SOURCE)
+ if (!vlan || READ_ONCE(vlan->mode) == MACVLAN_MODE_SOURCE)
return RX_HANDLER_PASS;
dev = vlan->dev;
@@ -548,7 +552,7 @@ static int macvlan_queue_xmit(struct sk_buff *skb, struct net_device *dev)
const struct macvlan_port *port = vlan->port;
const struct macvlan_dev *dest;
- if (vlan->mode == MACVLAN_MODE_BRIDGE) {
+ if (READ_ONCE(vlan->mode) == MACVLAN_MODE_BRIDGE) {
const struct ethhdr *eth = skb_eth_hdr(skb);
/* send to other bridge ports directly */
@@ -559,7 +563,7 @@ static int macvlan_queue_xmit(struct sk_buff *skb, struct net_device *dev)
}
dest = macvlan_hash_lookup(port, eth->h_dest);
- if (dest && dest->mode == MACVLAN_MODE_BRIDGE) {
+ if (dest && READ_ONCE(dest->mode) == MACVLAN_MODE_BRIDGE) {
/* send to lowerdev first for its network taps */
dev_forward_skb(vlan->lowerdev, skb);
@@ -777,7 +781,7 @@ static int macvlan_set_mac_address(struct net_device *dev, void *p)
if (ether_addr_equal(dev->dev_addr, addr->__data))
return 0;
- if (vlan->mode == MACVLAN_MODE_PASSTHRU) {
+ if (READ_ONCE(vlan->mode) == MACVLAN_MODE_PASSTHRU) {
macvlan_set_addr_change(vlan->port);
return dev_set_mac_address(vlan->lowerdev, addr, NULL);
}
@@ -1645,7 +1649,7 @@ static int macvlan_changelink(struct net_device *dev,
if (err < 0)
return err;
}
- vlan->flags = flags;
+ WRITE_ONCE(vlan->flags, flags);
}
if (data && data[IFLA_MACVLAN_BC_QUEUE_LEN]) {
@@ -1658,7 +1662,7 @@ static int macvlan_changelink(struct net_device *dev,
vlan, nla_get_s32(data[IFLA_MACVLAN_BC_CUTOFF]));
if (set_mode)
- vlan->mode = mode;
+ WRITE_ONCE(vlan->mode, mode);
if (data && data[IFLA_MACVLAN_MACADDR_MODE]) {
if (vlan->mode != MACVLAN_MODE_SOURCE)
return -EINVAL;
--
2.55.0.rc0.799.gd6f94ed593-goog
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH net-next 2/2] macvlan: no longer rely on RTNL in macvlan_fill_info()
2026-07-01 8:22 [PATCH net-next 0/2] macvlan: RTNL-less macvlan_fill_info() Eric Dumazet
2026-07-01 8:22 ` [PATCH net-next 1/2] macvlan: annotate data-races around vlan->mode and vlan->flags Eric Dumazet
@ 2026-07-01 8:22 ` Eric Dumazet
2026-07-01 12:11 ` Nikolay Aleksandrov
1 sibling, 1 reply; 5+ messages in thread
From: Eric Dumazet @ 2026-07-01 8:22 UTC (permalink / raw)
To: David S . Miller, Jakub Kicinski, Paolo Abeni
Cc: Simon Horman, Kuniyuki Iwashima, netdev, eric.dumazet,
Eric Dumazet
Add READ_ONCE()/WRITE_ONCE() annotations on vlan->mode, vlan->flags,
vlan->bc_queue_len_req and port->bc_cutoff.
Fill IFLA_MACVLAN_MACADDR_DATA nested attribute and compute
on the fly the precise number of elements we put in it,
to fill an accurate IFLA_MACVLAN_MACADDR_COUNT attribute
as some user space applications could depend on its value
and the attributes order.
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
drivers/net/macvlan.c | 71 +++++++++++++++++++++++++++++--------------
1 file changed, 48 insertions(+), 23 deletions(-)
diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 8b69cc9b70f98d7991110f5eda76d58d5d96fa81..9a4bc99dbf53b5f2cd6345f0af899f56fdb3a46b 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -171,7 +171,7 @@ static int macvlan_hash_add_source(struct macvlan_dev *vlan,
RCU_INIT_POINTER(entry->vlan, vlan);
h = &port->vlan_source_hash[macvlan_eth_hash(addr)];
hlist_add_head_rcu(&entry->hlist, h);
- vlan->macaddr_count++;
+ WRITE_ONCE(vlan->macaddr_count, vlan->macaddr_count + 1);
return 0;
}
@@ -402,7 +402,7 @@ static void macvlan_flush_sources(struct macvlan_port *port,
if (rcu_access_pointer(entry->vlan) == vlan)
macvlan_hash_del_source(entry);
- vlan->macaddr_count = 0;
+ WRITE_ONCE(vlan->macaddr_count, 0);
}
static void macvlan_forward_source_one(struct sk_buff *skb,
@@ -874,7 +874,7 @@ static void update_port_bc_cutoff(struct macvlan_dev *vlan, int cutoff)
if (vlan->port->bc_cutoff == cutoff)
return;
- vlan->port->bc_cutoff = cutoff;
+ WRITE_ONCE(vlan->port->bc_cutoff, cutoff);
macvlan_recompute_bc_filter(vlan);
}
@@ -1427,7 +1427,7 @@ static int macvlan_changelink_sources(struct macvlan_dev *vlan, u32 mode,
entry = macvlan_hash_lookup_source(vlan, addr);
if (entry) {
macvlan_hash_del_source(entry);
- vlan->macaddr_count--;
+ WRITE_ONCE(vlan->macaddr_count, vlan->macaddr_count - 1);
}
} else if (mode == MACVLAN_MACADDR_FLUSH) {
macvlan_flush_sources(vlan->port, vlan);
@@ -1653,7 +1653,8 @@ static int macvlan_changelink(struct net_device *dev,
}
if (data && data[IFLA_MACVLAN_BC_QUEUE_LEN]) {
- vlan->bc_queue_len_req = nla_get_u32(data[IFLA_MACVLAN_BC_QUEUE_LEN]);
+ WRITE_ONCE(vlan->bc_queue_len_req,
+ nla_get_u32(data[IFLA_MACVLAN_BC_QUEUE_LEN]));
update_port_bc_queue_len(vlan->port);
}
@@ -1676,10 +1677,12 @@ static int macvlan_changelink(struct net_device *dev,
static size_t macvlan_get_size_mac(const struct macvlan_dev *vlan)
{
- if (vlan->macaddr_count == 0)
+ unsigned int macaddr_count = READ_ONCE(vlan->macaddr_count);
+
+ if (!macaddr_count)
return 0;
return nla_total_size(0) /* IFLA_MACVLAN_MACADDR_DATA */
- + vlan->macaddr_count * nla_total_size(sizeof(u8) * ETH_ALEN);
+ + macaddr_count * nla_total_size(sizeof(u8) * ETH_ALEN);
}
static size_t macvlan_get_size(const struct net_device *dev)
@@ -1702,53 +1705,75 @@ static int macvlan_fill_info_macaddr(struct sk_buff *skb,
const int i)
{
struct hlist_head *h = &vlan->port->vlan_source_hash[i];
- struct macvlan_source_entry *entry;
+ const struct macvlan_source_entry *entry;
+ int cnt = 0;
- hlist_for_each_entry_rcu(entry, h, hlist, lockdep_rtnl_is_held()) {
+ hlist_for_each_entry_rcu(entry, h, hlist) {
if (rcu_access_pointer(entry->vlan) != vlan)
continue;
if (nla_put(skb, IFLA_MACVLAN_MACADDR, ETH_ALEN, entry->addr))
- return 1;
+ return -EMSGSIZE;
+ cnt++;
}
- return 0;
+ return cnt;
}
static int macvlan_fill_info(struct sk_buff *skb,
const struct net_device *dev)
{
- struct macvlan_dev *vlan = netdev_priv(dev);
+ const struct macvlan_dev *vlan = netdev_priv(dev);
struct macvlan_port *port = vlan->port;
- int i;
- struct nlattr *nest;
+ unsigned int macaddr_count = 0;
+ struct nlattr *nest, *attr;
+ int bc_cutoff, cnt, i;
- if (nla_put_u32(skb, IFLA_MACVLAN_MODE, vlan->mode))
+ rcu_read_lock();
+ if (nla_put_u32(skb, IFLA_MACVLAN_MODE, READ_ONCE(vlan->mode)))
goto nla_put_failure;
- if (nla_put_u16(skb, IFLA_MACVLAN_FLAGS, vlan->flags))
+
+ if (nla_put_u16(skb, IFLA_MACVLAN_FLAGS, READ_ONCE(vlan->flags)))
goto nla_put_failure;
- if (nla_put_u32(skb, IFLA_MACVLAN_MACADDR_COUNT, vlan->macaddr_count))
+
+ attr = nla_reserve(skb, IFLA_MACVLAN_MACADDR_COUNT, sizeof(u32));
+ if (!attr)
goto nla_put_failure;
- if (vlan->macaddr_count > 0) {
+
+ if (READ_ONCE(vlan->macaddr_count) > 0) {
nest = nla_nest_start_noflag(skb, IFLA_MACVLAN_MACADDR_DATA);
if (nest == NULL)
goto nla_put_failure;
for (i = 0; i < MACVLAN_HASH_SIZE; i++) {
- if (macvlan_fill_info_macaddr(skb, vlan, i))
+ cnt = macvlan_fill_info_macaddr(skb, vlan, i);
+ if (cnt < 0)
goto nla_put_failure;
+ macaddr_count += cnt;
}
- nla_nest_end(skb, nest);
+ if (!macaddr_count)
+ nla_nest_cancel(skb, nest);
+ else if (nla_nest_end_safe(skb, nest) < 0)
+ goto nla_put_failure;
}
- if (nla_put_u32(skb, IFLA_MACVLAN_BC_QUEUE_LEN, vlan->bc_queue_len_req))
+ *(u32 *)nla_data(attr) = macaddr_count;
+
+ if (nla_put_u32(skb, IFLA_MACVLAN_BC_QUEUE_LEN,
+ READ_ONCE(vlan->bc_queue_len_req)))
goto nla_put_failure;
+
if (nla_put_u32(skb, IFLA_MACVLAN_BC_QUEUE_LEN_USED,
READ_ONCE(port->bc_queue_len_used)))
goto nla_put_failure;
- if (port->bc_cutoff != 1 &&
- nla_put_s32(skb, IFLA_MACVLAN_BC_CUTOFF, port->bc_cutoff))
+
+ bc_cutoff = READ_ONCE(port->bc_cutoff);
+ if (bc_cutoff != 1 &&
+ nla_put_s32(skb, IFLA_MACVLAN_BC_CUTOFF, bc_cutoff))
goto nla_put_failure;
+
+ rcu_read_unlock();
return 0;
nla_put_failure:
+ rcu_read_unlock();
return -EMSGSIZE;
}
--
2.55.0.rc0.799.gd6f94ed593-goog
^ permalink raw reply related [flat|nested] 5+ messages in thread