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 B689F2882C9; Thu, 27 Nov 2025 14:52:00 +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=1764255120; cv=none; b=fe3KBHnurBd/QPno2TmiyGlRYXlgBwIGNr1xIqNEgWLsn2ZSIjN7vlROUYTHwMR7DDcSbm5AYj8XkNCB13IX3ocS7rTQhfiYODZ12xKlddEETJvBa8DYJmeVnzjQs+F++Oa7nS/BDSSm/a9hYSIptTahYdVQcIQ+Dbin+FIk/VM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764255120; c=relaxed/simple; bh=Q7xiEWAblFoYXQfS7zKq6u2Ua1nQeZVoBMXvF2y3/GI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JUHKxgA/WXPUzAC+aonFFzzHvvlqF6zmarTsnqo0nlfEYuZ5wiHP7gR6WOkTYSFb6IQR3E8N+5tigVjHndEa5V2J7R+DDQIPHheala3uOfJdQwyik7ROf52WW4iite7OzcSqriAHjCl9y2uH7CpW+Bd9qgbByBHDyVKsSpt+j2g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qyRWc43a; 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="qyRWc43a" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0BF14C4CEF8; Thu, 27 Nov 2025 14:51:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764255120; bh=Q7xiEWAblFoYXQfS7zKq6u2Ua1nQeZVoBMXvF2y3/GI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qyRWc43aXKAlq8uSYbEWI11kjOOdoI3LzYYNt3qww70KbaqR/MyGhHpUNZZrApg8i btna4urfq98rCvQvqDg/tEL1t1fTS+rLmy9rT0FWrRhaLAvrWl67Pos+KZqZJeedUV GIkEA+3KdmOCOo4gqJvEI2N3+OQ9jcaAmymc0pw8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jiayuan Chen , Martin KaFai Lau , Jakub Sitnicki , "Matthieu Baerts (NGI0)" Subject: [PATCH 6.12 015/112] mptcp: Fix proto fallback detection with BPF Date: Thu, 27 Nov 2025 15:45:17 +0100 Message-ID: <20251127144033.289954555@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251127144032.705323598@linuxfoundation.org> References: <20251127144032.705323598@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiayuan Chen commit c77b3b79a92e3345aa1ee296180d1af4e7031f8f upstream. The sockmap feature allows bpf syscall from userspace, or based on bpf sockops, replacing the sk_prot of sockets during protocol stack processing with sockmap's custom read/write interfaces. ''' tcp_rcv_state_process() syn_recv_sock()/subflow_syn_recv_sock() tcp_init_transfer(BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB) bpf_skops_established <== sockops bpf_sock_map_update(sk) <== call bpf helper tcp_bpf_update_proto() <== update sk_prot ''' When the server has MPTCP enabled but the client sends a TCP SYN without MPTCP, subflow_syn_recv_sock() performs a fallback on the subflow, replacing the subflow sk's sk_prot with the native sk_prot. ''' subflow_syn_recv_sock() subflow_ulp_fallback() subflow_drop_ctx() mptcp_subflow_ops_undo_override() ''' Then, this subflow can be normally used by sockmap, which replaces the native sk_prot with sockmap's custom sk_prot. The issue occurs when the user executes accept::mptcp_stream_accept::mptcp_fallback_tcp_ops(). Here, it uses sk->sk_prot to compare with the native sk_prot, but this is incorrect when sockmap is used, as we may incorrectly set sk->sk_socket->ops. This fix uses the more generic sk_family for the comparison instead. Additionally, this also prevents a WARNING from occurring: result from ./scripts/decode_stacktrace.sh: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 337 at net/mptcp/protocol.c:68 mptcp_stream_accept \ (net/mptcp/protocol.c:4005) Modules linked in: ... PKRU: 55555554 Call Trace: do_accept (net/socket.c:1989) __sys_accept4 (net/socket.c:2028 net/socket.c:2057) __x64_sys_accept (net/socket.c:2067) x64_sys_call (arch/x86/entry/syscall_64.c:41) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) RIP: 0033:0x7f87ac92b83d ---[ end trace 0000000000000000 ]--- Fixes: 0b4f33def7bb ("mptcp: fix tcp fallback crash") Signed-off-by: Jiayuan Chen Signed-off-by: Martin KaFai Lau Reviewed-by: Jakub Sitnicki Reviewed-by: Matthieu Baerts (NGI0) Cc: Link: https://patch.msgid.link/20251111060307.194196-3-jiayuan.chen@linux.dev Signed-off-by: Greg Kroah-Hartman --- net/mptcp/protocol.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -57,11 +57,13 @@ static u64 mptcp_wnd_end(const struct mp static const struct proto_ops *mptcp_fallback_tcp_ops(const struct sock *sk) { + unsigned short family = READ_ONCE(sk->sk_family); + #if IS_ENABLED(CONFIG_MPTCP_IPV6) - if (sk->sk_prot == &tcpv6_prot) + if (family == AF_INET6) return &inet6_stream_ops; #endif - WARN_ON_ONCE(sk->sk_prot != &tcp_prot); + WARN_ON_ONCE(family != AF_INET); return &inet_stream_ops; }