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 38669381AE7; Tue, 3 Mar 2026 18:07:06 +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=1772561226; cv=none; b=kd2Ivn/LjpyReLOG6jWSSq3727OLF+rhMFGXAzRCafyCEqmQDc9YPwCwGGAIiH63J6+gD6pjAjF1d2Ke9+5XU3YeT3uJ3MDagiIbagKYCt1g4G6QBEYO0jiOaifzlix3Z2qhMGLvcARDHllppeWtF5b7MDC9w9z23nIqJtxFE1k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772561226; c=relaxed/simple; bh=Vbtwpil7ZEF+eSxTpXm54O7ORfkDhNMpmIaREOK4zcI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=oK5PIIPxi7WqAJhpmbI1Vb6j2O8ni1f0Qlf22bVi0egpjz8hmarv/cj+TZYCp/bXqYVeP9x8rqOBl2vxB8TGoMkNmaYq7+YJDH8mfKyH1U3Vael212IJhhwNEevITX+sY+4GXpLfWCXb6u5w7HLsXM/k2e21Ah2iVRehc4ullZE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gFn59tBE; 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="gFn59tBE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7190EC116C6; Tue, 3 Mar 2026 18:07:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772561225; bh=Vbtwpil7ZEF+eSxTpXm54O7ORfkDhNMpmIaREOK4zcI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=gFn59tBETeDBUA4ZijYtktG36jO0BmtokcBGSoH8Vvwqk+6J0guotA+DUq3YEBN3U 0VBaK1uxB8KU4JbPjcYqI4wtgDqB+NeUqC5G+KES9ETvIbSAMyX6ctZZk6Bly29fER yPxsX2RiADfiV8E8bNq3GonralDGNaAGRu/vOSa2VtJjGMfRxEpuPCti4MunhM2Vya ++ODQNIf2ZMi4T7jfTn11yCbq6rhSPWAyHAAJTECg4KuBz6JoRM4i0Po/DhpcCmWaS geWX/n3/N7MgnWk/Yf0Zq8hEFUt937JN9Nuxf6FxrKggKcm1qYRCTz3MHQjCjoO3iF M27QDjKTLum2w== Message-ID: <57061768-a136-49b8-b020-609016f217ed@kernel.org> Date: Tue, 3 Mar 2026 19:06:59 +0100 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] mptcp: fix soft lockup in mptcp_recvmsg() Content-Language: en-GB, fr-BE To: Li Xiasong , martineau@kernel.org, geliang@kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org Cc: netdev@vger.kernel.org, mptcp@lists.linux.dev, linux-kernel@vger.kernel.org, weiyongjun1@huawei.com, yuehaibing@huawei.com, zhangchangzhong@huawei.com References: <20260302052651.1466983-1-lixiasong1@huawei.com> 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: <20260302052651.1466983-1-lixiasong1@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Li, On 02/03/2026 06:26, 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. (...) > Fixes: 612f71d7328c ("mptcp: fix possible stall on recvmsg()") > Signed-off-by: Li Xiasong > --- > net/mptcp/protocol.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c > index cf1852b99963..7a65c2101f63 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; > @@ -2058,6 +2058,8 @@ static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg, > } > > mptcp_eat_recv_skb(sk, skb); > + } else { > + *last = skb; Out of curiosity, why only setting *last for MSG_PEEK? Is it not better to always call sk_wait_data() later with the last skb, even when MSG_PEEK is not used? Or will this cause other troubles? > } > > if (copied >= len) > @@ -2263,6 +2265,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, > { > struct mptcp_sock *msk = mptcp_sk(sk); > struct scm_timestamping_internal tss; > + struct sk_buff *last = NULL; Detail: the scope of this variable could eventually be reduced by moving it inside the while-loop. This should hopefully help to reduce conflicts during backports. > int copied = 0, cmsg_flags = 0; > int target; > long timeo; > @@ -2291,7 +2294,8 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, > int err, bytes_read; > > bytes_read = __mptcp_recvmsg_mskq(sk, msg, len - copied, flags, > - copied, &tss, &cmsg_flags); > + copied, &tss, &cmsg_flags, > + &last); > if (unlikely(bytes_read < 0)) { > if (!copied) > copied = bytes_read; > @@ -2343,7 +2347,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, > > pr_debug("block timeout %ld\n", timeo); > mptcp_cleanup_rbuf(msk, copied); > - err = sk_wait_data(sk, &timeo, NULL); > + err = sk_wait_data(sk, &timeo, last); > if (err < 0) { > err = copied ? : err; > goto out_err; Cheers, Matt -- Sponsored by the NGI0 Core fund.