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 219B421770B; Thu, 27 Nov 2025 14:48:25 +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=1764254906; cv=none; b=anxc7NU4pOnJYVJhtcAXv9jNLCQIaOVO6LJQFi1po/SQCD2rW1UqCsYB/Batakq0eMU/gtf93uoAkwQ2KnRAo5IcVQuNZWUWaGrREm1RpGIzamooPQGY/luc9I67r/8x9b9FAGRYPpHkUr9tB9UlRPBKxTDJ+YqSRT6ZgVXBpQY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764254906; c=relaxed/simple; bh=JwCH0FGAJmKzOYm3doPmF7V49vkyU5wJaXMVszsSfuc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gukgfheXvTradwoioy/kRARfvg86rpvqAudiWu2vmHvyLERfqNJC+z+P5Ap1hRvkF+45C9zjWmkMuaZaQZD/m9yCZFPYq0xBLcB1GJimvDcc6TZ6xSsXDW89ar3vucjyr7uwKt81Q/v1Q4r8g9lkh2qnNJzZVj0pXzll6Ereljw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nRK9hA/u; 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="nRK9hA/u" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5E94FC4CEF8; Thu, 27 Nov 2025 14:48:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764254905; bh=JwCH0FGAJmKzOYm3doPmF7V49vkyU5wJaXMVszsSfuc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nRK9hA/uTncPJNM/y8rQsW+uRDoDlwbco0ydhRMHe9J/0vBMl40qZYgd8/wtxSNWS GCtRtUcdcZE53hpd9V4iGLesZg50Nmu84mE6+6GPu5skAyjxW0r2vr2AQ0qRa2wB2Z xZXwQogS7+m5iBlsdROzozYy8TUfsI8iV6Xidqxs= 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 6.6 08/86] mptcp: Fix proto fallback detection with BPF Date: Thu, 27 Nov 2025 15:45:24 +0100 Message-ID: <20251127144028.116430525@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251127144027.800761504@linuxfoundation.org> References: <20251127144027.800761504@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 6.6-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; }