From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2C21F2BEC5E; Mon, 13 Apr 2026 16:07:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776096447; cv=none; b=klxx/M7Sy3mFf01v7rKbUGc01ISO/6WKln4A6XRE0MSfy6mlAP2Ww03hXW6Jc/Dx0M4d2BuiMCMay0BSMvpLqr0PaFMuG2WU5cc9DglwPCogYcZii3hIc0vi7pmiAJyf5PnWkX969WwfWqdWCXFIi3OqSa2vwPhju0LBviPTQyA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776096447; c=relaxed/simple; bh=g2i81jZysxNwjtJ3A2WW5Z98i3A4MqYCivlU0kAnBng=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NMqcjkD5qIA/9nqo1qtvYs4x+/kQXybndXajHZoL3TjZYIfkHSkbascDDJ1EkiRoja1jao7GRXPh8ybUGUUx8vzd7I7Z+d+8VRmj7s/EdLUOttgd7nZI2cSe/BcYqAZz74Yah1KFy+RND+sgAk8uNurgi7PF3WHfYXgt1C9RIDg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=d4gQYQqI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="d4gQYQqI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B601CC2BCB0; Mon, 13 Apr 2026 16:07:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1776096447; bh=g2i81jZysxNwjtJ3A2WW5Z98i3A4MqYCivlU0kAnBng=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=d4gQYQqIwobHKKIom+TOyYGkUjB2pNkO7micHKekjmBw49cqpbUWjUtoqEwUmjM/l 1Mll7KMYddRacCP4T2dv75/UeL5iI+avOzHkabLTSbjXhOfv8o0vo2ekJn3ZlQtdun 9aP3MwaEmnXcdaYG25mfqgbptDDGI0DCiTrLWGMw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jiayuan Chen , "Matthieu Baerts (NGI0)" , Jakub Kicinski Subject: [PATCH 6.18 07/83] mptcp: fix slab-use-after-free in __inet_lookup_established Date: Mon, 13 Apr 2026 17:59:35 +0200 Message-ID: <20260413155731.304371373@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260413155731.019638460@linuxfoundation.org> References: <20260413155731.019638460@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiayuan Chen commit 9b55b253907e7431210483519c5ad711a37dafa1 upstream. The ehash table lookups are lockless and rely on SLAB_TYPESAFE_BY_RCU to guarantee socket memory stability during RCU read-side critical sections. Both tcp_prot and tcpv6_prot have their slab caches created with this flag via proto_register(). However, MPTCP's mptcp_subflow_init() copies tcpv6_prot into tcpv6_prot_override during inet_init() (fs_initcall, level 5), before inet6_init() (module_init/device_initcall, level 6) has called proto_register(&tcpv6_prot). At that point, tcpv6_prot.slab is still NULL, so tcpv6_prot_override.slab remains NULL permanently. This causes MPTCP v6 subflow child sockets to be allocated via kmalloc (falling into kmalloc-4k) instead of the TCPv6 slab cache. The kmalloc-4k cache lacks SLAB_TYPESAFE_BY_RCU, so when these sockets are freed without SOCK_RCU_FREE (which is cleared for child sockets by design), the memory can be immediately reused. Concurrent ehash lookups under rcu_read_lock can then access freed memory, triggering a slab-use-after-free in __inet_lookup_established. Fix this by splitting the IPv6-specific initialization out of mptcp_subflow_init() into a new mptcp_subflow_v6_init(), called from mptcp_proto_v6_init() before protocol registration. This ensures tcpv6_prot_override.slab correctly inherits the SLAB_TYPESAFE_BY_RCU slab cache. Fixes: b19bc2945b40 ("mptcp: implement delegated actions") Cc: stable@vger.kernel.org Signed-off-by: Jiayuan Chen Reviewed-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260406031512.189159-1-jiayuan.chen@linux.dev Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/mptcp/protocol.c | 2 ++ net/mptcp/protocol.h | 1 + net/mptcp/subflow.c | 15 +++++++++------ 3 files changed, 12 insertions(+), 6 deletions(-) --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -4271,6 +4271,8 @@ int __init mptcp_proto_v6_init(void) { int err; + mptcp_subflow_v6_init(); + mptcp_v6_prot = mptcp_prot; strscpy(mptcp_v6_prot.name, "MPTCPv6", sizeof(mptcp_v6_prot.name)); mptcp_v6_prot.slab = NULL; --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -830,6 +830,7 @@ static inline void mptcp_subflow_tcp_fal void __init mptcp_proto_init(void); #if IS_ENABLED(CONFIG_MPTCP_IPV6) int __init mptcp_proto_v6_init(void); +void __init mptcp_subflow_v6_init(void); #endif struct sock *mptcp_sk_clone_init(const struct sock *sk, --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -2145,7 +2145,15 @@ void __init mptcp_subflow_init(void) tcp_prot_override.psock_update_sk_prot = NULL; #endif + mptcp_diag_subflow_init(&subflow_ulp_ops); + + if (tcp_register_ulp(&subflow_ulp_ops) != 0) + panic("MPTCP: failed to register subflows to ULP\n"); +} + #if IS_ENABLED(CONFIG_MPTCP_IPV6) +void __init mptcp_subflow_v6_init(void) +{ /* In struct mptcp_subflow_request_sock, we assume the TCP request sock * structures for v4 and v6 have the same size. It should not changed in * the future but better to make sure to be warned if it is no longer @@ -2184,10 +2192,5 @@ void __init mptcp_subflow_init(void) /* Disable sockmap processing for subflows */ tcpv6_prot_override.psock_update_sk_prot = NULL; #endif -#endif - - mptcp_diag_subflow_init(&subflow_ulp_ops); - - if (tcp_register_ulp(&subflow_ulp_ops) != 0) - panic("MPTCP: failed to register subflows to ULP\n"); } +#endif