[PATCH net-next v4 1/7] 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
every entry is checked against the entry policy up front, before any
entry is acted on. A message whose entry the policy rejects -- a
malformed attribute, or, with the next patch, an out-of-range endpoint
-- is now refused as a unit and installs nothing. Faults the policy does
not cover, such as a device or handler error raised on a later entry,
are unchanged: entries are still dispatched and applied one at a time.

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>
---
v4: scope the "rejected as a unit" claim to
policy-rejected entries; rebased onto net-next.

 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 41095096b698..124ba47758e9 100644
--- a/drivers/net/vxlan/vxlan_vnifilter.c
+++ b/drivers/net/vxlan/vxlan_vnifilter.c
@@ -499,7 +499,7 @@ 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),
 };
 
 bool vxlan_vnifilter_has_multicast(const struct vxlan_dev *vxlan)

base-commit: 05b5019b01fb9443b09ae4ed34af1135a80a84c8
-- 
2.53.0