[PATCH net] tipc: reject name table updates with invalid origin node

[PATCH net] tipc: reject name table updates with invalid origin node

[Jun Yang]

From: Jun Yang <junvyyang@tencent.com>

tipc_update_nametbl() trusts the origin node carried in a received
NAME_DISTRIBUTOR message. For a WITHDRAWAL it removes and frees the
matching publication with tipc_nametbl_remove_publ() (a {key,ref}
wildcard match that ignores the node), then calls
tipc_node_unsubscribe() to unlink the publication from the advertising
node's publ_list.

tipc_node_unsubscribe() is a no-op when in_own_node(net, node) is true,
and in_own_node() treats node 0 as "own" (addr == own || !addr). So a
WITHDRAWAL with orignode == 0 frees the publication via kfree_rcu()
while the paired unsubscribe silently does nothing, leaving the freed
publication linked on the owning peer's publ_list through its
binding_node.

A subsequent legitimate WITHDRAWAL for a neighbouring publication that
the same peer advertised then performs list_del() across the freed
object, writing a kernel pointer into freed memory (use-after-free
write) and corrupting the live publ_list head. The whole sequence is
attacker-driven from received packets and is reachable by an
unprivileged local user, who can gain CAP_NET_ADMIN in a new network
namespace via unshare(CLONE_NEWUSER|CLONE_NEWNET), enable a TIPC UDP
bearer, and emulate a peer over loopback UDP.

A name table update must always originate from a real peer node, never
from our own address or from node 0. Reject such updates up front:
in_own_node() already covers both cases, so a single guard at the top
of tipc_update_nametbl() drops the malformed update before any
publication is removed or freed.

Fixes: 37922ea4a310 ("tipc: permit overlapping service ranges in name table")
Cc: stable@kernel.org
Reported-by: TencentOS Corvus AI <corvus@tencent.com>
Signed-off-by: Jun Yang <junvyyang@tencent.com>
---
 net/tipc/name_distr.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/tipc/name_distr.c b/net/tipc/name_distr.c
index ba4f4906e13b..a496e2e9ef62 100644
--- a/net/tipc/name_distr.c
+++ b/net/tipc/name_distr.c
@@ -286,6 +286,9 @@ static bool tipc_update_nametbl(struct net *net, struct distr_item *i,
 	u32 key = ntohl(i->key);
 	struct tipc_uaddr ua;
 
+	if (in_own_node(net, node))
+		return false;
+
 	/* A peer-advertised binding with lower > upper can never be matched
 	 * or withdrawn and would leak the publication; the local bind path
 	 * rejects such ranges, so reject ranges learned from the network too.
-- 
2.55.0