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 F23762C08D4; Thu, 23 Oct 2025 14:10:52 +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=1761228653; cv=none; b=eIPAqdCNtivXbaNRYOe28O/Mos3mUY08WLmPtXkO4YPBhhZ4DjN6r7Q8wFYiWRjc8lFu15G7pmCVpbU7Tks8CNCF25p+ItqAynu7u3r5jN6Pr755AnYTr2RBgDiRCXiPehGNBNJMJDl0z7gCzjFhnyYog01uGHbyBJSaduQnrn0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761228653; c=relaxed/simple; bh=9j/Nj79fZM+lECIfYOli/ze3SV2mU/GUWdoAbKY6Buw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JZSRgND/JtsEhbwV4njA4dxX4icvGll89cmuYeX63Ok33o2RbnaKvpF9Veq8uaf1/gwQV8cTt3m02cV5ejnI66ecm5o8kqaw75yt7UpI2a9yn9uZwj8xrWCKFKcPoZvSBYGrqOcgm+F8ehJSAAo0WjeTqc+Vuq9KtysdB1KtCN4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ErQg4Paz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ErQg4Paz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33EEFC4CEE7; Thu, 23 Oct 2025 14:10:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761228652; bh=9j/Nj79fZM+lECIfYOli/ze3SV2mU/GUWdoAbKY6Buw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ErQg4Paz3kRBPlWuFBJhWREpNcYlrqM42mVImWxF51ZtNphxKiFWKubBtEqQUX68g vHlRrVz8lHY9SkBxlx/t+MMB2m0PcTjn3SRfAsJf+cmoUYkDIFvsrgYRi/tCcfD7m7 7xlMXSbi5JZpO/qaMZdGOEXIhYtUPeC7k+AxXFM93nE0hwU/IfF9BlYdXRIWcor5Uu tKryLCFNLtUNA8yyZV/uQSezNnUKd7xE6ETEs/44TjtvpZChyxHx1y3H2akaHn2PGQ kjPTwrpTHH5zZr/ZpvzRccv6NC9xLVyxtwqBaNiEvDUm5CV3M2ty2rFFWiQOkHbgiR msA4vpFoWW8Ug== Message-ID: Date: Thu, 23 Oct 2025 16:10:41 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v3 1/3] net,mptcp: fix proto fallback detection with BPF sockmap Content-Language: en-GB, fr-BE To: Jiayuan Chen , mptcp@lists.linux.dev Cc: stable@vger.kernel.org, Jakub Sitnicki , John Fastabend , Eric Dumazet , Kuniyuki Iwashima , Paolo Abeni , Willem de Bruijn , "David S. Miller" , Jakub Kicinski , Simon Horman , Mat Martineau , Geliang Tang , Andrii Nakryiko , Eduard Zingerman , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , Florian Westphal , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20251023125450.105859-1-jiayuan.chen@linux.dev> <20251023125450.105859-2-jiayuan.chen@linux.dev> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; keydata= xsFNBFXj+ekBEADxVr99p2guPcqHFeI/JcFxls6KibzyZD5TQTyfuYlzEp7C7A9swoK5iCvf YBNdx5Xl74NLSgx6y/1NiMQGuKeu+2BmtnkiGxBNanfXcnl4L4Lzz+iXBvvbtCbynnnqDDqU c7SPFMpMesgpcu1xFt0F6bcxE+0ojRtSCZ5HDElKlHJNYtD1uwY4UYVGWUGCF/+cY1YLmtfb WdNb/SFo+Mp0HItfBC12qtDIXYvbfNUGVnA5jXeWMEyYhSNktLnpDL2gBUCsdbkov5VjiOX7 CRTkX0UgNWRjyFZwThaZADEvAOo12M5uSBk7h07yJ97gqvBtcx45IsJwfUJE4hy8qZqsA62A nTRflBvp647IXAiCcwWsEgE5AXKwA3aL6dcpVR17JXJ6nwHHnslVi8WesiqzUI9sbO/hXeXw TDSB+YhErbNOxvHqCzZEnGAAFf6ges26fRVyuU119AzO40sjdLV0l6LE7GshddyazWZf0iac nEhX9NKxGnuhMu5SXmo2poIQttJuYAvTVUNwQVEx/0yY5xmiuyqvXa+XT7NKJkOZSiAPlNt6 VffjgOP62S7M9wDShUghN3F7CPOrrRsOHWO/l6I/qJdUMW+MHSFYPfYiFXoLUZyPvNVCYSgs 3oQaFhHapq1f345XBtfG3fOYp1K2wTXd4ThFraTLl8PHxCn4ywARAQABzSRNYXR0aGlldSBC YWVydHMgPG1hdHR0YmVAa2VybmVsLm9yZz7CwZEEEwEIADsCGwMFCwkIBwIGFQoJCAsCBBYC AwECHgECF4AWIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZUDpDAIZAQAKCRD2t4JPQmmgcz33 EACjROM3nj9FGclR5AlyPUbAq/txEX7E0EFQCDtdLPrjBcLAoaYJIQUV8IDCcPjZMJy2ADp7 /zSwYba2rE2C9vRgjXZJNt21mySvKnnkPbNQGkNRl3TZAinO1Ddq3fp2c/GmYaW1NWFSfOmw MvB5CJaN0UK5l0/drnaA6Hxsu62V5UnpvxWgexqDuo0wfpEeP1PEqMNzyiVPvJ8bJxgM8qoC cpXLp1Rq/jq7pbUycY8GeYw2j+FVZJHlhL0w0Zm9CFHThHxRAm1tsIPc+oTorx7haXP+nN0J iqBXVAxLK2KxrHtMygim50xk2QpUotWYfZpRRv8dMygEPIB3f1Vi5JMwP4M47NZNdpqVkHrm jvcNuLfDgf/vqUvuXs2eA2/BkIHcOuAAbsvreX1WX1rTHmx5ud3OhsWQQRVL2rt+0p1DpROI 3Ob8F78W5rKr4HYvjX2Inpy3WahAm7FzUY184OyfPO/2zadKCqg8n01mWA9PXxs84bFEV2mP VzC5j6K8U3RNA6cb9bpE5bzXut6T2gxj6j+7TsgMQFhbyH/tZgpDjWvAiPZHb3sV29t8XaOF BwzqiI2AEkiWMySiHwCCMsIH9WUH7r7vpwROko89Tk+InpEbiphPjd7qAkyJ+tNIEWd1+MlX ZPtOaFLVHhLQ3PLFLkrU3+Yi3tXqpvLE3gO3LM7BTQRV4/npARAA5+u/Sx1n9anIqcgHpA7l 5SUCP1e/qF7n5DK8LiM10gYglgY0XHOBi0S7vHppH8hrtpizx+7t5DBdPJgVtR6SilyK0/mp 9nWHDhc9rwU3KmHYgFFsnX58eEmZxz2qsIY8juFor5r7kpcM5dRR9aB+HjlOOJJgyDxcJTwM 1ey4L/79P72wuXRhMibN14SX6TZzf+/XIOrM6TsULVJEIv1+NdczQbs6pBTpEK/G2apME7vf mjTsZU26Ezn+LDMX16lHTmIJi7Hlh7eifCGGM+g/AlDV6aWKFS+sBbwy+YoS0Zc3Yz8zrdbi Kzn3kbKd+99//mysSVsHaekQYyVvO0KD2KPKBs1S/ImrBb6XecqxGy/y/3HWHdngGEY2v2IP Qox7mAPznyKyXEfG+0rrVseZSEssKmY01IsgwwbmN9ZcqUKYNhjv67WMX7tNwiVbSrGLZoqf Xlgw4aAdnIMQyTW8nE6hH/Iwqay4S2str4HZtWwyWLitk7N+e+vxuK5qto4AxtB7VdimvKUs x6kQO5F3YWcC3vCXCgPwyV8133+fIR2L81R1L1q3swaEuh95vWj6iskxeNWSTyFAVKYYVskG V+OTtB71P1XCnb6AJCW9cKpC25+zxQqD2Zy0dK3u2RuKErajKBa/YWzuSaKAOkneFxG3LJIv Hl7iqPF+JDCjB5sAEQEAAcLBXwQYAQIACQUCVeP56QIbDAAKCRD2t4JPQmmgc5VnD/9YgbCr HR1FbMbm7td54UrYvZV/i7m3dIQNXK2e+Cbv5PXf19ce3XluaE+wA8D+vnIW5mbAAiojt3Mb 6p0WJS3QzbObzHNgAp3zy/L4lXwc6WW5vnpWAzqXFHP8D9PTpqvBALbXqL06smP47JqbyQxj Xf7D2rrPeIqbYmVY9da1KzMOVf3gReazYa89zZSdVkMojfWsbq05zwYU+SCWS3NiyF6QghbW voxbFwX1i/0xRwJiX9NNbRj1huVKQuS4W7rbWA87TrVQPXUAdkyd7FRYICNW+0gddysIwPoa KrLfx3Ba6Rpx0JznbrVOtXlihjl4KV8mtOPjYDY9u+8x412xXnlGl6AC4HLu2F3ECkamY4G6 UxejX+E6vW6Xe4n7H+rEX5UFgPRdYkS1TA/X3nMen9bouxNsvIJv7C6adZmMHqu/2azX7S7I vrxxySzOw9GxjoVTuzWMKWpDGP8n71IFeOot8JuPZtJ8omz+DZel+WCNZMVdVNLPOd5frqOv mpz0VhFAlNTjU1Vy0CnuxX3AM51J8dpdNyG0S8rADh6C8AKCDOfUstpq28/6oTaQv7QZdge0 JY6dglzGKnCi/zsmp2+1w559frz4+IC7j/igvJGX4KDDKUs0mlld8J2u2sBXv7CGxdzQoHaz lzVbFe7fduHbABmYz9cefQpO7wDE/Q== Organization: NGI0 Core In-Reply-To: <20251023125450.105859-2-jiayuan.chen@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Jiayuan, On 23/10/2025 14:54, Jiayuan Chen wrote: > When the server has MPTCP enabled but receives a non-MP-capable request > from a client, it calls mptcp_fallback_tcp_ops(). > > Since non-MPTCP connections are allowed to use sockmap, which replaces > sk->sk_prot, using sk->sk_prot to determine the IP version in > mptcp_fallback_tcp_ops() becomes unreliable. This can lead to assigning > incorrect ops to sk->sk_socket->ops. > > Additionally, when BPF Sockmap modifies the protocol handlers, the > original WARN_ON_ONCE(sk->sk_prot != &tcp_prot) check would falsely > trigger warnings. > > Fix this by using the more stable sk_family to distinguish between IPv4 > and IPv6 connections, ensuring correct fallback protocol operations are > selected even when BPF Sockmap has modified the socket protocol handlers. > > Fixes: 0b4f33def7bb ("mptcp: fix tcp fallback crash") > Cc: > Signed-off-by: Jiayuan Chen > Reviewed-by: Jakub Sitnicki > --- > net/mptcp/protocol.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c > index 0292162a14ee..2393741bc310 100644 > --- a/net/mptcp/protocol.c > +++ b/net/mptcp/protocol.c > @@ -61,11 +61,16 @@ static u64 mptcp_wnd_end(const struct mptcp_sock *msk) > > static const struct proto_ops *mptcp_fallback_tcp_ops(const struct sock *sk) > { > + /* When BPF sockmap is used, it may replace sk->sk_prot. > + * Using sk_family is a reliable way to determine the IP version. > + */ > + 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; Just to be sure: is there anything in BPF modifying sk->sk_socket->ops? Because that's what mptcp_fallback_tcp_ops() will do somehow. In other words, is it always fine to set inet(6)_stream_ops? (I guess yes, but better to be sure while we are looking at that :) ) > } > Cheers, Matt -- Sponsored by the NGI0 Core fund.