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 A32DE13A244; Sat, 4 Apr 2026 11:15:53 +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=1775301353; cv=none; b=sCmcL+6F/wyJhjTWKcdtoXord+ZqSiWrkcCReigAG1KZxDu1UjSaWrWjz3CWzeCqNeYLClPaQbRMN4VMoEKPtBp8scUzWVwjFuVUukgrpJ/Q7P8AOdXCuW05Z9kNXZ+piCneeKU/d8gg6Q+iCsQbRF4V1mRYrz7WX9C72hP2CDk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775301353; c=relaxed/simple; bh=dfhS9tV3KlRfmBCVpT5htf8yf6i8XgWSpM3gUYk0qWk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LlNrkEDnAHtJamrmd8GIuTErwbvm/P/bHoZW3ML6cbWxs4NlB17UcJsq37E6aTlzP0SLg1OCiHVQAPjg8C/bPwVI1AFdub4NKPiDiH3QuTPrsSS+yxIxe+av1o2JVgSnINDeQY/yNCosjcBS6Vr9NOD88NMAXlfmNQlO2ExlHns= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GwtaKlBJ; 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="GwtaKlBJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DBFCCC19421; Sat, 4 Apr 2026 11:15:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775301353; bh=dfhS9tV3KlRfmBCVpT5htf8yf6i8XgWSpM3gUYk0qWk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=GwtaKlBJIXQLC2Q1qlJfoy66lVd3RzR/HmkcPFa8cZwECSrdGio9g1mEFcR+Cs0hT qD4dW7pYiXAQSkCLItdKycoIJerG4l3kEnvvR+LXDO7B+yynqa4ONeSkDI3IgBkKi8 J3jQ8CmXAD5F7n8jZ78DPLgk8hPcZp9kIEqzNna3NrIVN1KZJFE19Uiq/eMyrokoIh lx/yVj7zlsFoGhy9FXnRqdpHn7NWcaV5vJ0hVC+xMFSNHMuWm7u5OMlQmVwDryvETh cT3BwHM20PQTdsbrKdM/wHe0/HPcE+zwpN5ykqDQOTPLIyRfE69+7RJ1ZXYeyb11Xj tOa3aUZWwQJUA== Message-ID: <9791b7d2-734b-4148-ad7b-89a374420a9c@kernel.org> Date: Sat, 4 Apr 2026 13:15:47 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH net v1] net: mptcp: fix slab-use-after-free in __inet_lookup_established Content-Language: fr To: Jiayuan Chen , mptcp@lists.linux.dev, netdev@vger.kernel.org Cc: Mat Martineau , Geliang Tang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-kernel@vger.kernel.org References: <20260403130734.93981-1-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: <20260403130734.93981-1-jiayuan.chen@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Jiayuan, On 03/04/2026 15:07, Jiayuan Chen wrote: > The ehash table lookups are lockless and rely on > SLAB_TYPESAFE_BY_RCU to guarantee socket memory stability > during RCU read-side critical sections. Both tcp_prot and > tcpv6_prot have their slab caches created with this flag > via proto_register(). > > However, MPTCP's mptcp_subflow_init() copies tcpv6_prot into > tcpv6_prot_override during inet_init() (fs_initcall, level 5), > before inet6_init() (module_init/device_initcall, level 6) has > called proto_register(&tcpv6_prot). At that point, > tcpv6_prot.slab is still NULL, so tcpv6_prot_override.slab > remains NULL permanently. > > This causes MPTCP v6 subflow child sockets to be allocated via > kmalloc (falling into kmalloc-4k) instead of the TCPv6 slab > cache. The kmalloc-4k cache lacks SLAB_TYPESAFE_BY_RCU, so > when these sockets are freed without SOCK_RCU_FREE (which is > cleared for child sockets by design), the memory can be > immediately reused. Concurrent ehash lookups under > rcu_read_lock can then access freed memory, triggering a > slab-use-after-free in __inet_lookup_established. Good catch! Thank you for this patch. > Fix this by splitting the IPv6-specific initialization out of > mptcp_subflow_init() into a new mptcp_subflow_v6_init(), which > is called from mptcpv6_init() after proto_register(&tcpv6_prot) > has completed. This ensures tcpv6_prot_override.slab correctly > inherits the SLAB_TYPESAFE_BY_RCU slab cache. The split makes sense anyway: better to regroup all v6-related init steps. > Fixes: b19bc2945b40 ("mptcp: implement delegated actions") > Signed-off-by: Jiayuan Chen > --- > net/mptcp/ctrl.c | 6 +++++- > net/mptcp/protocol.h | 1 + > net/mptcp/subflow.c | 15 +++++++++------ > 3 files changed, 15 insertions(+), 7 deletions(-) > > diff --git a/net/mptcp/ctrl.c b/net/mptcp/ctrl.c > index d96130e49942..5887ddcdb875 100644 > --- a/net/mptcp/ctrl.c > +++ b/net/mptcp/ctrl.c > @@ -583,7 +583,11 @@ int __init mptcpv6_init(void) > int err; > > err = mptcp_proto_v6_init(); > + if (err) > + return err; > > - return err; > + mptcp_subflow_v6_init(); I think it would be better to move this to mptcp_proto_v6_init, similar to what is done with mptcp_subflow_init, from mptcp_proto_init. >From there, you can even call it before registering the protocol, at the beginning, so before inet6_register_protosw, which seems more logical and similar to what is done in v4. WDYT? If you send a v2, can you please remove the 'net:' prefix please? 'mptcp:' is enough: [PATCH net v2] mptcp: fix (...) Also, can you add a "Cc: stable" tag please? Cheers, Matt -- Sponsored by the NGI0 Core fund.