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 65A991A9FAF for ; Mon, 24 Nov 2025 13:22:58 +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=1763990578; cv=none; b=UZWldQo1zy8bh86D9RKpYJ+1uqabQPwrkpKx4DAuwBk3I3790stFtaYMGJ3Gsx9eU5zmZgZwPZ4wHIXYennATN6TkJyeq9rfWsHC/4oJlOAm0Ww1a2496F62P0cJfM32sCJW2XuTLUViX1EzQDP47Y3OADqpBLbcz2K5fShQ1kE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763990578; c=relaxed/simple; bh=HdUFXLh134/eS6u4h1HRIJQy4oITtkkNA5T7YZYXUYI=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=Q+wjGEA0Uu1c/Rht+cT+46H2d3I+RRIJZJHmMaEln1aYXbE7CoMKhrqrtI2CwVR3DnZbq7rrx61hgvmO5D4jBjVwPZcZWJKf6nw787V1PRIFhB/D43SIQlOuJ72qFJvBCcmmKJLl0Lk8HUh+5QcfzfwetUCVRXBLa66fzDYwBR0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XFrx3Ak8; 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="XFrx3Ak8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 80DDEC19421; Mon, 24 Nov 2025 13:22:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1763990577; bh=HdUFXLh134/eS6u4h1HRIJQy4oITtkkNA5T7YZYXUYI=; h=Subject:To:Cc:From:Date:From; b=XFrx3Ak8XadazV1eGivK7VDAtNS60wOE1rQbgj3Y4d23cMTs7s0cHWYCbZ7pIsQxV Sl2UJNu5uNONEECxTtQDEMk/3dBZ8NToH2Wtixd7j/sekA4c2j+Teaml+kw9dF5jWm dAJq/i27EnfA1Bl7wkaeVkh8A0iTT629epZdi0VU= Subject: FAILED: patch "[PATCH] mptcp: Fix proto fallback detection with BPF" failed to apply to 5.10-stable tree To: jiayuan.chen@linux.dev,jakub@cloudflare.com,martin.lau@kernel.org,matttbe@kernel.org,stable@vger.kernel.org Cc: From: Date: Mon, 24 Nov 2025 14:22:55 +0100 Message-ID: <2025112454-comic-external-4ced@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x c77b3b79a92e3345aa1ee296180d1af4e7031f8f # git commit -s git send-email --to '' --in-reply-to '2025112454-comic-external-4ced@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From c77b3b79a92e3345aa1ee296180d1af4e7031f8f Mon Sep 17 00:00:00 2001 From: Jiayuan Chen Date: Tue, 11 Nov 2025 14:02:51 +0800 Subject: [PATCH] mptcp: Fix proto fallback detection with BPF 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 diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 2d6b8de35c44..90b4aeca2596 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -61,11 +61,13 @@ static u64 mptcp_wnd_end(const struct mptcp_sock *msk) 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; }