[PATCH net-next v3 1/6] vxlan: vnifilter: validate the VXLAN_VNIFILTER_ENTRY nest

[Ali Firas <alishmery18@gmail.com>]

vxlan_vnifilter_process() parses the message with vni_filter_policy,
whose VXLAN_VNIFILTER_ENTRY is a bare NLA_NESTED with no nested policy
attached. The entry attributes are therefore validated only later, one
entry at a time, by the nla_parse_nested() inside
vxlan_process_vni_filter(). Entries are parsed as they are dispatched:
in a message whose first entry is valid and whose second is not, the
first entry is applied and its RTM_NEWTUNNEL notification sent before
the second is rejected.

Link the nest to vni_filter_entry_policy with NLA_POLICY_NESTED() so the
whole message is validated up front, before any entry is acted on. A
message carrying an invalid entry is now rejected as a unit and installs
nothing.

This reorders two faults. The nest is validated before the device is
looked up and before the vnifilter flag is checked, so a request
rejected by the entry policy, aimed at a missing or non-vnifilter
device, now returns that policy error where it previously returned
-ENODEV or -EOPNOTSUPP. The request was invalid either way; only the
errno an operator sees changes.

The nla_parse_nested() in vxlan_process_vni_filter() stays: it is what
fills the per-entry attribute table the handler reads. It can no longer
fail on a message that has reached it.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/netdev/20260921150904.65a704eb@kernel.org/
Assisted-by: LLM
Signed-off-by: Ali Firas <alishmery18@gmail.com>
---

Notes:
    v3: new patch. Link the nest with NLA_POLICY_NESTED(), as Jakub asked.

 drivers/net/vxlan/vxlan_vnifilter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/vxlan/vxlan_vnifilter.c b/drivers/net/vxlan/vxlan_vnifilter.c
index dd94085e0886..d391ec579661 100644
--- a/drivers/net/vxlan/vxlan_vnifilter.c
+++ b/drivers/net/vxlan/vxlan_vnifilter.c
@@ -467,7 +467,7 @@ static const struct nla_policy vni_filter_entry_policy[VXLAN_VNIFILTER_ENTRY_MAX
 };
 
 static const struct nla_policy vni_filter_policy[VXLAN_VNIFILTER_MAX + 1] = {
-	[VXLAN_VNIFILTER_ENTRY] = { .type = NLA_NESTED },
+	[VXLAN_VNIFILTER_ENTRY] = NLA_POLICY_NESTED(vni_filter_entry_policy),
 };
 
 static int vxlan_update_default_fdb_entry(struct vxlan_dev *vxlan, __be32 vni,
-- 
2.53.0