[PATCH net v3 1/3] tipc: require net admin for TIPCv2 netlink mutators

[Michael Bommarito <michael.bommarito@gmail.com>]

TIPCv2 registers mutating generic-netlink operations without admin
permission flags. Generic netlink only checks CAP_NET_ADMIN when an
operation sets GENL_ADMIN_PERM or GENL_UNS_ADMIN_PERM, so a local
unprivileged process can currently change TIPC state through commands
such as TIPC_NL_NET_SET, TIPC_NL_KEY_SET, TIPC_NL_KEY_FLUSH, and
bearer enable/disable.

The legacy TIPC netlink API already checks netlink_net_capable(...,
CAP_NET_ADMIN) for administrative commands. Give the TIPCv2 mutators
the equivalent generic-netlink gate. Use GENL_UNS_ADMIN_PERM for
network-namespace scoped operations and GENL_ADMIN_PERM for
TIPC_NL_MEDIA_SET, which updates the shared media defaults rather than
state owned only by the target network namespace.

A QEMU/KASAN repro run as uid/gid 65534 with zero effective
capabilities previously succeeded in changing the network id and node
identity, setting and flushing key material, and enabling/disabling a
UDP bearer. With this patch applied the same operations fail with
-EPERM.

Fixes: 0655f6a8635b ("tipc: add bearer disable/enable to new netlink api")
Link: https://lore.kernel.org/all/20260604163102.2658553-1-dominik.czarnota@trailofbits.com/
Assisted-by: Codex:gpt-5-5-xhigh
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
---
v2:
- Use GENL_ADMIN_PERM for TIPC_NL_MEDIA_SET because it updates global
  media defaults, while keeping GENL_UNS_ADMIN_PERM for netns-scoped
  mutators.

 net/tipc/netlink.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/net/tipc/netlink.c b/net/tipc/netlink.c
index 1a9a5bdaccf4f..5bbe134284acc 100644
--- a/net/tipc/netlink.c
+++ b/net/tipc/netlink.c
@@ -152,11 +152,13 @@ static const struct genl_ops tipc_genl_v2_ops[] = {
 	{
 		.cmd	= TIPC_NL_BEARER_DISABLE,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= tipc_nl_bearer_disable,
 	},
 	{
 		.cmd	= TIPC_NL_BEARER_ENABLE,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= tipc_nl_bearer_enable,
 	},
 	{
@@ -168,11 +170,13 @@ static const struct genl_ops tipc_genl_v2_ops[] = {
 	{
 		.cmd	= TIPC_NL_BEARER_ADD,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= tipc_nl_bearer_add,
 	},
 	{
 		.cmd	= TIPC_NL_BEARER_SET,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= tipc_nl_bearer_set,
 	},
 	{
@@ -197,11 +201,13 @@ static const struct genl_ops tipc_genl_v2_ops[] = {
 	{
 		.cmd	= TIPC_NL_LINK_SET,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= tipc_nl_node_set_link,
 	},
 	{
 		.cmd	= TIPC_NL_LINK_RESET_STATS,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit   = tipc_nl_node_reset_link_stats,
 	},
 	{
@@ -213,6 +219,7 @@ static const struct genl_ops tipc_genl_v2_ops[] = {
 	{
 		.cmd	= TIPC_NL_MEDIA_SET,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_ADMIN_PERM,
 		.doit	= tipc_nl_media_set,
 	},
 	{
@@ -228,6 +235,7 @@ static const struct genl_ops tipc_genl_v2_ops[] = {
 	{
 		.cmd	= TIPC_NL_NET_SET,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= tipc_nl_net_set,
 	},
 	{
@@ -238,6 +246,7 @@ static const struct genl_ops tipc_genl_v2_ops[] = {
 	{
 		.cmd	= TIPC_NL_MON_SET,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= tipc_nl_node_set_monitor,
 	},
 	{
@@ -255,6 +264,7 @@ static const struct genl_ops tipc_genl_v2_ops[] = {
 	{
 		.cmd	= TIPC_NL_PEER_REMOVE,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= tipc_nl_peer_rm,
 	},
 #ifdef CONFIG_TIPC_MEDIA_UDP
@@ -269,11 +279,13 @@ static const struct genl_ops tipc_genl_v2_ops[] = {
 	{
 		.cmd	= TIPC_NL_KEY_SET,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= tipc_nl_node_set_key,
 	},
 	{
 		.cmd	= TIPC_NL_KEY_FLUSH,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= tipc_nl_node_flush_key,
 	},
 #endif
-- 
2.53.0