From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793211761; b=PP9UdiD83ROqivFh8DPfB8WsaOSxkWk5znApgzfy7Bxryj1XbZ2fP3q+pu91rnd7OnN7 4Lt93g1KSq+KjLVZIJAWEraxiRSJGNrF1q3z0SbnnrYMWtkW6juhFKiMb/xPslJHP7Oll tEzzJmNUwKCbHHjp7jkIhjfCzhXzFkw8Ot52LKjBAu6CmB+m/5qZ0kG8HxhKnAv5gS7+L HrzyqCfCXK4DGYJ7AjBEUW1kiTXnyE955HuXEUY/3MtLzw4SXorIiWmb9v6jvDCoPptFr HCzATtRGobRGmyRqF1+oLhVqvG2sLq3aUDnOxzIToKgockF4Q1Kiin3o7CJdN1TqWfg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793211761; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=F8hK+uRlz6uA9zEX3Hy7AsbQ+HH8RzQQgMoIWTNPW3M=; b=vn5so073KVZ6ayjns8LV02QB1iFzlAcAV/YeL9sDMw29dZ9kZBKC9q8qyJSDkFnDB0Q+ 5l/j+8yLyCA40dlVKk78I3MR8UcwJ80UQ+6+KN8CRBNrExfMfLlZUvskWXHuj3ngR3fYf b4EEx+hItlml/q6JedWfyyBFT7RYlkUDMgE8ZWWy9BAtdRG2j5UxPBi12o8ZkM6vcvMAy zBh930LGKo+sWwj+cZmuoNFQNT6EgqmuP5IoJyoojh/iKqACwAryiQUoLKB/SaK30/RL0 TjRUzKcVSiysBWrCOp58MScw+/9zgTZPpXz5/GWeQzhqMTeEtKMmVeNpWtXXaDFrJ0w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=dalieIoX; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1617B606A326; Wed, 28 Oct 2026 18:22:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=dalieIoX Received: by smtp.kernel.org (Postfix) with ESMTPSA id 63BED1F01825; Wed, 28 Oct 2026 18:22:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793211760; bh=F8hK+uRlz6uA9zEX3Hy7AsbQ+HH8RzQQgMoIWTNPW3M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dalieIoXCb72i5sssHVoJqbePDJzucaD2dvV2p0JhyMTFnaCbQQmqIgq0Ggb1FhPj az+MdKm2LYYGhKcqFH4u1q/RF/fOB9DJx59BkAUCHPoA9KEEIOeQqYdY8zkmNJJvOa lAUZWqjEpquQd9NmxeS7IO/y+kr8ch6ge79pv/gc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kyle Zeng , Simon Horman , Eric Dumazet , Paolo Abeni , Sasha Levin Subject: [PATCH 5.15 491/571] netlink: avoid hashing the network namespace pointer Date: Wed, 28 Oct 2026 18:00:38 +0100 Message-ID: <20261028170019.679844597@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170008.009143722@linuxfoundation.org> References: <20261028170008.009143722@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kyle Zeng [ Upstream commit f88bb3606e4bd11ee035b682cddc2999e604609a ] The netlink rhashtable key includes a raw struct net pointer and a user-controlled port ID. Both /proc/net/netlink and socket diagnostics expose the table's bucket order. By binding and rebinding chosen NETLINK_USERSOCK port IDs, an unprivileged reader can distinguish equal buckets and recover the low bits of the Jenkins hash. Its 32-bit seed and the limited set of kernel-image slides can then be searched offline to recover the address of init_net. Use the namespace's unique, non-address net_cookie in the comparison key instead. It is assigned before the per-net initializers run and remains unchanged for the namespace's lifetime. The lookup key and object hash are still built by netlink_compare_arg_init(), keeping lookup, insertion, removal and rehashing consistent while preserving namespace separation. Neither public table walker needs to change. Reading the socket's namespace cookie in netlink_compare() is safe under RCU, including during namespace teardown. netlink_release() removes the socket from the hash table and defers its final put with call_rcu(). cleanup_net() runs the per-net exit methods and waits for outstanding RCU callbacks with rcu_barrier() before freeing namespace storage. Unlike ns.ns_id, net_cookie is also available and initialized during setup_net() in older stable kernels, making the change straightforward to backport to v5.15 and later. Fixes: c428ecd1a21f ("netlink: Move namespace into hash key") Assisted-by: LLM Signed-off-by: Kyle Zeng Reviewed-by: Simon Horman Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20261008011359.63727-2-kylebot@openai.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- net/netlink/af_netlink.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 63065d2449509..3671071482a02 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -463,7 +463,7 @@ netlink_unlock_table(void) struct netlink_compare_arg { - possible_net_t pnet; + u64 net_cookie; u32 portid; }; @@ -478,14 +478,14 @@ static inline int netlink_compare(struct rhashtable_compare_arg *arg, const struct netlink_sock *nlk = ptr; return nlk->portid != x->portid || - !net_eq(sock_net(&nlk->sk), read_pnet(&x->pnet)); + sock_net(&nlk->sk)->net_cookie != x->net_cookie; } static void netlink_compare_arg_init(struct netlink_compare_arg *arg, struct net *net, u32 portid) { memset(arg, 0, sizeof(*arg)); - write_pnet(&arg->pnet, net); + arg->net_cookie = net->net_cookie; arg->portid = portid; } -- 2.53.0