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 5C63F2E091E; Tue, 24 Mar 2026 19:23:41 +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=1774380221; cv=none; b=kKhGMAEa1jZTSmIfYcqXzs0JSBl10Evd2CRO4isK3MPo2uhcUlEqXu15imyq4xei/t2J6Uee5HiPAoTEWTqdYj9X7UodJ8fWT3xEhjPo8h7CxSVqA3AAYQ9E5ITnRWgKJbbVESQrDxiGBBq6XWCshn4UU/jju79tdtD2Dt/c30E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774380221; c=relaxed/simple; bh=M6BaYp+o6NW7QEKfWc+kQxWN0t/QRnWTE0dlOGQ3QyY=; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:References: In-Reply-To:Content-Type; b=IMz/5W3Ne9ZIgHnJVm4nBrzS9jIWPkPxrT+Kx78EIB3P04NJhzxvGVA4Ai763Gae6YZSI/LGrQUdul5aPLyXI2Iyx5Mkd3DgMKiPh5v2zrMLu0dKjleu7cYuHqWkXmRfL1asM1V6IxWo/CTjbrXtgjRrNSVAonifTfclkk5SSBQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XgTQWuyu; 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="XgTQWuyu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B381C19424; Tue, 24 Mar 2026 19:23:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774380221; bh=M6BaYp+o6NW7QEKfWc+kQxWN0t/QRnWTE0dlOGQ3QyY=; h=Date:From:Subject:To:Cc:References:In-Reply-To:From; b=XgTQWuyu9PtYdh07P2VXFwTdXiL4+5kvn45rWh57bK4R1NVFS7Me9ZZcUBfPNhWL1 i3xrDU62ZroJfzS9H0dax4EJvzh4/iYYVwxBcD987HUfu/6eKLaz0E6Q7cyeqoiLFh bvhbi0rAwUIZX2l6PjU38L4haJTDx6S8gdDcDrul1g6lZMfU23EnhDbJGmrkHo1PGQ OidigxWIePAhuVfzNtssSKrV4Mm5iqndg6etYThUyykUm/gGWjOrNbg49zBhLJq9Wp SokWsXVkWMJUppJ10zbpJv7R9xZqK+fwpRhSLC+x32hMKJgm8Nzbr0bl3guwhHkSCI yW7QN4k992Frg== Message-ID: <12ad947e-f386-4fcc-9043-bf4f95a7db83@kernel.org> Date: Tue, 24 Mar 2026 20:23:33 +0100 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 From: Matthieu Baerts Subject: Re: [PATCH net v2] mptcp: fix soft lockup in mptcp_recvmsg() To: Li Xiasong , Mat Martineau , Geliang Tang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: netdev@vger.kernel.org, mptcp@lists.linux.dev, linux-kernel@vger.kernel.org, yuehaibing@huawei.com, zhangchangzhong@huawei.com, weiyongjun1@huawei.com References: <20260324085131.4187473-1-lixiasong1@huawei.com> Content-Language: fr 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: <20260324085131.4187473-1-lixiasong1@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Li, On 24/03/2026 09:51, Li Xiasong wrote: > syzbot reported a soft lockup in mptcp_recvmsg() [0]. > > When receiving data with MSG_PEEK | MSG_WAITALL flags, the skb is not > removed from the sk_receive_queue. This causes sk_wait_data() to always > find available data and never perform actual waiting, leading to a soft > lockup. > > Fix this by adding a 'last' parameter to track the last peeked skb. > This allows sk_wait_data() to make informed waiting decisions and prevent > infinite loops when MSG_PEEK is used. (...) > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c > index cf1852b99963..401fb2b17685 100644 > --- a/net/mptcp/protocol.c > +++ b/net/mptcp/protocol.c > @@ -2006,7 +2006,7 @@ static void mptcp_eat_recv_skb(struct sock *sk, struct sk_buff *skb) > static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg, > size_t len, int flags, int copied_total, > struct scm_timestamping_internal *tss, > - int *cmsg_flags) > + int *cmsg_flags, struct sk_buff **last) > { > struct mptcp_sock *msk = mptcp_sk(sk); > struct sk_buff *skb, *tmp; > @@ -2048,6 +2048,7 @@ static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg, > } > > copied += count; > + *last = skb; My bad, my recommendation to move this assignment here was not a good idea, because 'skb' can be freed at some points after mptcp_eat_recv_skb that can be called here below. If I'm not mistaken, when MSG_PEEK is not used, sk_wait_data() can always be called with NULL for the last skb, because the queue is supposed to be empty. If not, no need to wait for new packets, so NULL can be used. Is that correct? If yes, then I guess 'last' can be initialised to NULL before calling __mptcp_recvmsg_mskq (limit scope), and only set to 'skb' here below, when MSG_PEEK is not used (what you had in v1). Would that work for you? Cheers, Matt -- Sponsored by the NGI0 Core fund.