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=1792774026; b=sXZAt8o9WBz0SrP7TTnP7G0i54xX7KcINRmyg3lhrOziwdG0piatDvhuTD7WSTPR7sYH cQtD9ybfhPiGzTPpkj3x6qv2Q2GD/3Pbm4hIC+XssdMV2v1Ojj6QPVJ5aoGtNABwjH/vS XmBUA2Xg8xCn164g35fMtzkLHgYeQMJNF+4W8ep5Qdtcp/MMNEpj2OaDWY6MTJDXllrHG zAgSyOTRKxrUgy7XT2wm4p5dTHEPOD2lYGAa/IIaomyG6wL6PM4r6IUtjqKH8cd3REn2G 3IoVL+C2xARpDjEJJKab0dBsIoh36VLuiV/6Wd7EZADN1YqZJyPFp1C4V1hHK1oLWNQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792774026; 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=fRececC8v2Sl6jxGLA9dSW6jJ8Zw6P4pMQLEaeSi0d8=; b=cBwx+bTJ3cV4XjB5bCv3MZzbNtdW1DYmWdFRlA4lT13FYegiMPqfU7gy0qFSde7DctGq CGkgny/UKdkCNHaaYJUlJjesk8yS0Zu2c8OWmcPLCO4aTxd6MfygLg23liIMraNvg8VKl wbHCtXP82UJ+rZFvNAQuVdKE73KTxAwDPnGkZZdy+syEVNfikh/EodOSnQcPcj0RcMvJf P7k5B12A1Fn5hu8X7VqbMLiQdFtqDiwWqZVXMf0eQA7yLQxrxokG8uASvTROPsbrrQ/tD giisUp1SfDURnLshI98VXovCljbIyA2TaPEkzAznbtLof32pgvhbg3EZZQeaJO0WZoA== 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="00X/SKCq"; 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 8706F606A31D; Fri, 23 Oct 2026 16:47:06 +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=00X/SKCq Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7CBE1F01825; Fri, 23 Oct 2026 16:47:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792774026; bh=fRececC8v2Sl6jxGLA9dSW6jJ8Zw6P4pMQLEaeSi0d8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=00X/SKCqjA41ToZAmeI6ZrjvkiOUIvdYd26ddXgAK3h5hOtgGW5mW2G+mlIVLBN+b zkZcy6a8xqU3Wh5v9cUf2jOPrUGFE62NIYZTT8lTnEaoZi1HL0RjmYLlo6xrXGGgXw gkFhCDNXw8w7nR1VHEFVpGiGSbWPBtXDMZZ5SD14= 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 6.18 058/193] netlink: avoid hashing the network namespace pointer Date: Fri, 23 Oct 2026 18:35:35 +0200 Message-ID: <20261023163715.578351217@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261023163714.201276352@linuxfoundation.org> References: <20261023163714.201276352@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 6.18-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 c41fef11e518f..6c0aabca5dbad 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