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macvlan: fix possible UAF in macvlan_forward_source()

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Add RCU protection on (struct macvlan_source_entry)->vlan.

Whenever macvlan_hash_del_source() is called, we must clear
entry->vlan pointer before RCU grace period starts.

This allows macvlan_forward_source() to skip over
entries queued for freeing.

Note that macvlan_dev are already RCU protected, as they
are embedded in a standard netdev (netdev_priv(ndev)).

Fixes: 79cf79abce ("macvlan: add source mode")
Reported-by: syzbot+7182fbe91e58602ec1fe@syzkaller.appspotmail.com
https: //lore.kernel.org/netdev/695fb1e8.050a0220.1c677c.039f.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260108133651.1130486-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet
2026-01-08 13:36:51 +00:00
committed by Jakub Kicinski
parent eb74c19fe1
commit 7470a7a63d
1 changed files with 13 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

20
drivers/net/macvlan.c
View File

@@ -59,7 +59,7 @@ struct macvlan_port {
struct macvlan_source_entry {
struct hlist_node hlist;
struct macvlan_dev *vlan;
struct macvlan_dev __rcu *vlan;
unsigned char addr[6+2] __aligned(sizeof(u16));
struct rcu_head rcu;
};
@@ -146,7 +146,7 @@ static struct macvlan_source_entry *macvlan_hash_lookup_source(
hlist_for_each_entry_rcu(entry, h, hlist, lockdep_rtnl_is_held()) {
if (ether_addr_equal_64bits(entry->addr, addr) &&
entry->vlan == vlan)
rcu_access_pointer(entry->vlan) == vlan)
return entry;
}
return NULL;
@@ -168,7 +168,7 @@ static int macvlan_hash_add_source(struct macvlan_dev *vlan,
return -ENOMEM;
ether_addr_copy(entry->addr, addr);
entry->vlan = 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++;
@@ -187,6 +187,7 @@ static void macvlan_hash_add(struct macvlan_dev *vlan)
static void macvlan_hash_del_source(struct macvlan_source_entry *entry)
{
RCU_INIT_POINTER(entry->vlan, NULL);
hlist_del_rcu(&entry->hlist);
kfree_rcu(entry, rcu);
}
@@ -390,7 +391,7 @@ static void macvlan_flush_sources(struct macvlan_port *port,
int i;
hash_for_each_safe(port->vlan_source_hash, i, next, entry, hlist)
if (entry->vlan == vlan)
if (rcu_access_pointer(entry->vlan) == vlan)
macvlan_hash_del_source(entry);
vlan->macaddr_count = 0;
@@ -433,9 +434,14 @@ static bool macvlan_forward_source(struct sk_buff *skb,
hlist_for_each_entry_rcu(entry, h, hlist) {
if (ether_addr_equal_64bits(entry->addr, addr)) {
if (entry->vlan->flags & MACVLAN_FLAG_NODST)
struct macvlan_dev *vlan = rcu_dereference(entry->vlan);
if (!vlan)
continue;
if (vlan->flags & MACVLAN_FLAG_NODST)
consume = true;
macvlan_forward_source_one(skb, entry->vlan);
macvlan_forward_source_one(skb, vlan);
}
}
@@ -1680,7 +1686,7 @@ static int macvlan_fill_info_macaddr(struct sk_buff *skb,
struct macvlan_source_entry *entry;
hlist_for_each_entry_rcu(entry, h, hlist, lockdep_rtnl_is_held()) {
if (entry->vlan != vlan)
if (rcu_access_pointer(entry->vlan) != vlan)
continue;
if (nla_put(skb, IFLA_MACVLAN_MACADDR, ETH_ALEN, entry->addr))
return 1;