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 774E21A275 for ; Mon, 24 Nov 2025 13:21:57 +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=1763990517; cv=none; b=UPJm3J4yOmIQrIn8Js8/I2++73z1jvRDiY+IuQ7Xh13fUlS0J4g/HZdUXfE2WfpuiddwyZax5NJvaQYaDOWjxXgiCtTnhful5WAsDpdraX50jeTiDAtGe720MUShGZJs7NLKtJF/+j1rh23L0Nr9OvYwQBUocqtqx5WGIAsxk98= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763990517; c=relaxed/simple; bh=WW93j2nFBA8ADyjMW8HmIApTWu7egXdWyIROV5YeyI8=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=iGm+4OkFDtjYQZnutWt22ZcRmeGAfr54LGtD+881AS4LkOIneN8tDkGWr8tUerteLdP7wW4UPYnJp4NVwoNysboFkUy4Hei6JUUaDFuSMOveUUSHJjy1qyjuem8nlss5OLrp9iOJYdenxLXIFcsW1jWyU+uR2dl82yVsxDlJEGk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=f8jdyP+x; 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="f8jdyP+x" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AA155C4CEF1; Mon, 24 Nov 2025 13:21:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1763990517; bh=WW93j2nFBA8ADyjMW8HmIApTWu7egXdWyIROV5YeyI8=; h=Subject:To:Cc:From:Date:From; b=f8jdyP+xc2Q5BJOaEzOaI+stEWdMb0CRV9F/rioz0fB5RvQxQgPB7taVBpgYxAMUn IEjHVInjbT91m3z4pv6xHHJ8bMf/fS/RVa7ytoB3CVrw4sNukPTQJDVKGMTjEmKbub HzSw/wrIzNEHIhTBaj1Ub8Uyu6iBG9W+G7QhSGSs= Subject: FAILED: patch "[PATCH] mptcp: Disallow MPTCP subflows from sockmap" failed to apply to 5.15-stable tree To: jiayuan.chen@linux.dev,martin.lau@kernel.org,matttbe@kernel.org,stable@vger.kernel.org Cc: From: Date: Mon, 24 Nov 2025 14:21:54 +0100 Message-ID: <2025112454-crib-recognize-8675@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 5.15-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-5.15.y git checkout FETCH_HEAD git cherry-pick -x fbade4bd08ba52cbc74a71c4e86e736f059f99f7 # git commit -s git send-email --to '' --in-reply-to '2025112454-crib-recognize-8675@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From fbade4bd08ba52cbc74a71c4e86e736f059f99f7 Mon Sep 17 00:00:00 2001 From: Jiayuan Chen Date: Tue, 11 Nov 2025 14:02:50 +0800 Subject: [PATCH] mptcp: Disallow MPTCP subflows from sockmap 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() 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 ''' Consider two scenarios: 1. When the server has MPTCP enabled and the client also requests MPTCP, the sk passed to the BPF program is a subflow sk. Since subflows only handle partial data, replacing their sk_prot is meaningless and will cause traffic disruption. 2. 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_ulp_fallback() subflow_drop_ctx() mptcp_subflow_ops_undo_override() ''' Subsequently, accept::mptcp_stream_accept::mptcp_fallback_tcp_ops() converts the subflow to plain TCP. For the first case, we should prevent it from being combined with sockmap by setting sk_prot->psock_update_sk_prot to NULL, which will be blocked by sockmap's own flow. For the second case, since subflow_syn_recv_sock() has already restored sk_prot to native tcp_prot/tcpv6_prot, no further action is needed. Fixes: cec37a6e41aa ("mptcp: Handle MP_CAPABLE options for outgoing connections") Signed-off-by: Jiayuan Chen Signed-off-by: Martin KaFai Lau Reviewed-by: Matthieu Baerts (NGI0) Cc: Link: https://patch.msgid.link/20251111060307.194196-2-jiayuan.chen@linux.dev diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index e8325890a322..af707ce0f624 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -2144,6 +2144,10 @@ void __init mptcp_subflow_init(void) tcp_prot_override = tcp_prot; tcp_prot_override.release_cb = tcp_release_cb_override; tcp_prot_override.diag_destroy = tcp_abort_override; +#ifdef CONFIG_BPF_SYSCALL + /* Disable sockmap processing for subflows */ + tcp_prot_override.psock_update_sk_prot = NULL; +#endif #if IS_ENABLED(CONFIG_MPTCP_IPV6) /* In struct mptcp_subflow_request_sock, we assume the TCP request sock @@ -2180,6 +2184,10 @@ void __init mptcp_subflow_init(void) tcpv6_prot_override = tcpv6_prot; tcpv6_prot_override.release_cb = tcp_release_cb_override; tcpv6_prot_override.diag_destroy = tcp_abort_override; +#ifdef CONFIG_BPF_SYSCALL + /* Disable sockmap processing for subflows */ + tcpv6_prot_override.psock_update_sk_prot = NULL; +#endif #endif mptcp_diag_subflow_init(&subflow_ulp_ops);