netdev - [PATCH net-next 3/9] l2tp: fix handling of hash key collisions in l2tp_v3_session

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Message-Id: <fbc3d1e3d57c644b97a238168a200c79a2ec8c98.1722856576.git.jchapman@katalix.com>
Date: Mon,  5 Aug 2024 12:35:27 +0100
From: James Chapman <jchapman@...alix.com>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	dsahern@...nel.org,
	tparkin@...alix.com
Subject: [PATCH net-next 3/9] l2tp: fix handling of hash key collisions in l2tp_v3_session_get

To handle colliding l2tpv3 session IDs, l2tp_v3_session_get searches a
hashed list keyed by ID and sk. Although unlikely, if hash keys
collide, it is possible that hash_for_each_possible loops over a
session which doesn't have the ID that we are searching for. So check
for session ID match when looping over possible hash key matches.

Fixes: aa5e17e1f5ec ("l2tp: store l2tpv3 sessions in per-net IDR")
Signed-off-by: James Chapman <jchapman@...alix.com>
Signed-off-by: Tom Parkin <tparkin@...alix.com>
---
 net/l2tp/l2tp_core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 5d2068b6c778..0c661d499a6f 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -286,7 +286,8 @@ struct l2tp_session *l2tp_v3_session_get(const struct net *net, struct sock *sk,
 			 */
 			struct l2tp_tunnel *tunnel = READ_ONCE(session->tunnel);
 
-			if (tunnel && tunnel->sock == sk &&
+			if (session->session_id == session_id &&
+			    tunnel && tunnel->sock == sk &&
 			    refcount_inc_not_zero(&session->ref_count)) {
 				rcu_read_unlock_bh();
 				return session;
-- 
2.34.1