From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-179.mta0.migadu.com (out-179.mta0.migadu.com [91.218.175.179]) (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 C155234887C for ; Mon, 6 Apr 2026 03:15:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775445339; cv=none; b=jCmruRm4fpxAnyz54cmT4LnwdHL/DSzMlj2N9COUJd8klKx/a8lS2p7uR3eiAahqkq+KJKvM5fqHSqWC/9KdtI2Mz5y6s32hHPgPOem74+quaUQI2bFFaxMxUW9PYKXihmscZGxbIV8AEtkva3xzgZMVK9s/Lx351nx9axHq8hU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775445339; c=relaxed/simple; bh=VnKcRhtnXmg3esTxutvPiewGjUarJqAT10kc4eGYok4=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=i0JE7TRaqHjJHlzNHgmXyHVM5agqdmjsCI++i6nVmfgROb3GyLDIjareRj8zjBk9Fy262N+PRlqYwQjn9Ipz+lvDRv9mRA2zVj3qbmcHJkmT6A1QabCMyS0IffpHgDMDFqCSwxBW7IAxYn2ymVQhGVlp7T4B3i7mwSVjLykdWNU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=qMppkvCP; arc=none smtp.client-ip=91.218.175.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="qMppkvCP" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1775445324; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=pCU31PuVLxnkqkH0Q/gfVj7NOZB8sp1JJeyWvm+opn0=; b=qMppkvCPiJYh+m7P00Vul4Jo2KsY7FUMAzJ7JHiQ0AAMkRusLuXvkSBInX0nzNiYSiQzSi 5b+yway8muyT9Hoxbv+KK5va66DvhgtG8FHI00LQa7y1qzFsZpRn2Eb+FmaX8rQRzaDKxI l/HKg/HyeNDl9AP70zAEPbpR2S9VYWo= From: Jiayuan Chen To: mptcp@lists.linux.dev Cc: Jiayuan Chen , stable@vger.kernel.org, Matthieu Baerts , Mat Martineau , Geliang Tang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net v2] mptcp: fix slab-use-after-free in __inet_lookup_established Date: Mon, 6 Apr 2026 11:15:10 +0800 Message-ID: <20260406031512.189159-1-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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 --- net/mptcp/protocol.c | 2 ++ net/mptcp/protocol.h | 1 + net/mptcp/subflow.c | 15 +++++++++------ 3 files changed, 12 insertions(+), 6 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 65c3bb8016f4..614c3f583ca0 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -4660,6 +4660,8 @@ 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; diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 0bd1ee860316..ec15e503da8b 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -875,6 +875,7 @@ static inline void mptcp_subflow_tcp_fallback(struct sock *sk, 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, diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 6716970693e9..4ff5863aa9fd 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -2165,7 +2165,15 @@ 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 @@ -2204,10 +2212,5 @@ 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 -- 2.43.0