From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 C3A64369D63; Mon, 10 Aug 2026 10:01:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786356116; cv=none; b=qeQdReHnzHRzRRfpZg7jpGj0EZMyluIl5BxM6Z9/MiG/l2GxreuX17WivEY7VMoo7JPhHN2c2F3PAapHxXgI3XVwmlwMPIW0fDnGO88vymterFDE1GRs6qBaOITbaAGObuDGkYQeUvmW5tau8F8QpP7ptmor74zU1po296fWRlg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786356116; c=relaxed/simple; bh=2u7WR45fdwk7K/czlnqoUIfX37QB1Gg2xz8pc35hIU8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KrseMG5UDCx7QQ8NwWnToHqPZWGO3E3C1JM+0+XGhw8VTKzZI7ubrFNxdRpxJAq+hB763FpnrrKFucVwqQXzJOSLJnXYkT/A2AHxROsSN0pbGVTCLlen13/2I+wHeEPwXCJapwzqJTEWNQYlBZGo15z8CKfi+yDmrh3A/0rRahE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iOBl2NVz; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iOBl2NVz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AFCE31F000E9; Mon, 10 Aug 2026 10:01:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786356114; bh=HW3GX6I3wLPnT6+ysjemWmbbHJD7ingYVdNWRjY+rhA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=iOBl2NVzxlO09qwfYE3kn2bUuIVS9Y4zppQAYDx8oB2rgRp2Tbgk+xphWyERzl9WE Yybk277qlZbSdmIeb1m4DrpLQx4S21iBARl4mVG5Trn1wVAzHKOisIn48UcNzdvBMl pUcYWy2EAJmCY6TzQDi7lYBuKz7pzdPZODl2XoSzTu3wJeiMocMrcm3UMzUBSKW4+f uBa9DC8RMyB7MqhGLcmjYArk2U6VngwuKIoV6q8bRZDr5Ux+cgE64MY5YXr8+9u4yi bt772TXdY2m98ViwsnHhO3kZ5tCK3fcptPOR00m1wlcZXZZcfzOQn/lzLLFNN7/B7f KwGa5Vayjb1CQ== Message-ID: <8d1f2ccc-df93-41b0-9873-a159aca7c03c@kernel.org> Date: Mon, 10 Aug 2026 12:01:47 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH net] mptcp: upgrade network refcount before socket lock Content-Language: fr To: Runyu Xiao , Mat Martineau Cc: Geliang Tang , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , mptcp@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, jianhao.xu@seu.edu.cn, stable@vger.kernel.org References: <20260809091949.3618191-1-runyu.xiao@seu.edu.cn> 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: <20260809091949.3618191-1-runyu.xiao@seu.edu.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Runyu, On 09/08/2026 11:19, Runyu Xiao wrote: > sk_net_refcnt_upgrade() calls get_net_track() with GFP_KERNEL and can enter > direct reclaim. Calling it while holding the newly created subflow socket > lock can create a reclaim-to-socket-lock dependency cycle. > > Upgrade the network reference before taking the socket lock. The socket is > newly created and has not been exposed to other code at this point, so the > fields changed by sk_net_refcnt_upgrade() are not accessed concurrently. > The error path still releases the socket normally after the upgrade. Thank you for the patch! Even if I agree with Gang that the commit message could be improved, the code looks good to me, and probably best not to increase the traffic on the netdev list. So it looks good to me: Reviewed-by: Matthieu Baerts (NGI0) @Net maintainers: this patch can be applied to net directly. > The PatchProof static-analysis tool detected a GFP_KERNEL allocation while > the socket lock is held. Manual source review of v7.1.5 and current > mainline confirmed the lock and allocation ordering. > > A source-level check found `sk_net_refcnt_upgrade()` after > `lock_sock_nested()` in the original function and before it after this > change. A POSIX-thread lock-order model made the reclaim lock unavailable > while the socket lock was held, observed `EBUSY` for the reclaim lock, and > then completed with the reclaim-first order. The model checks the ordering > invariant only; it does not execute the kernel MPTCP path. No live lockdep > MPTCP test or reclaim fault injection was run. Interesting. By chance, any reproducer to share? Cheers, Matt -- Sponsored by the NGI0 Core fund.