From nobody Sun Mar 22 08:27:52 2026 Received: from canpmsgout10.his.huawei.com (canpmsgout10.his.huawei.com [113.46.200.225]) (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 9F5511B4F1F for ; Mon, 2 Mar 2026 05:02:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.225 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772427750; cv=none; b=Pk0kMAZxhxnQ6PacN1JA7vmjMXVfo9RfKzm2UJ8+T8bOs2KAdjq02KRefH8nPZfaGdaNHYVMc4zp8u2HXCe8vTa8rcO27PhfTe5dCKxKA7tLzEEcrmOL/H7boArmxUdQfs/BZHDCknzoVGYWrzhPoAS0znWuhVvAJtZevgKle3E= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772427750; c=relaxed/simple; bh=JSLnltizuRPn6CwAgjoGO+dMG3OxBLRggzZpbQ0Yo+s=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=RYNApKa/GvFM3H92/l4snGt6wGaUuJ+i3MKgl2E5FZkhE0tIRm06iYekAFg9Nm2Tbm9HO4WwHeggEX80yt1bhqoN6YJttbD1jYQEIkITjUmCA7e3bSloKldM62UOotI9OMKQhunPX/uwp/CWc1E50bIi/TMg62PODrsKGC9PAFo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=nDsbAAS9; arc=none smtp.client-ip=113.46.200.225 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="nDsbAAS9" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=SI9FLDsxgn0wLMHqZBnpavtvFfxk9bqG169b2B7HPLg=; b=nDsbAAS9abg2NHjngiv/ohaxfqN1V/WnTI06HSjcUqzRbWNRtAp6PiC81yK2XcuOihzJlby/V IaqqrgvzdkBNWwxP9UOXATJm6y4BZ99K4h/SwgCtYHWdvVbA6bPyGUZ7pXyk9O1d4Xb9+fN+Z2C VgOuaUj1tNjkNrKraUfHSbk= Received: from mail.maildlp.com (unknown [172.19.163.15]) by canpmsgout10.his.huawei.com (SkyGuard) with ESMTPS id 4fPRWH0KB8z1K97f; Mon, 2 Mar 2026 12:57:31 +0800 (CST) Received: from kwepemj500018.china.huawei.com (unknown [7.202.194.48]) by mail.maildlp.com (Postfix) with ESMTPS id 7B8D140565; Mon, 2 Mar 2026 13:02:18 +0800 (CST) Received: from huawei.com (10.50.85.128) by kwepemj500018.china.huawei.com (7.202.194.48) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 2 Mar 2026 13:02:17 +0800 From: Li Xiasong To: , , , , , , , CC: , , , , , Subject: [PATCH net] mptcp: fix soft lockup in mptcp_recvmsg() Date: Mon, 2 Mar 2026 13:26:51 +0800 Message-ID: <20260302052651.1466983-1-lixiasong1@huawei.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: kwepems500001.china.huawei.com (7.221.188.70) To kwepemj500018.china.huawei.com (7.202.194.48) Content-Type: text/plain; charset="utf-8" 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. [0]: watchdog: BUG: soft lockup - CPU#2 stuck for 156s! [server:1963] Modules linked in: CPU: 2 UID: 0 PID: 1963 Comm: server Not tainted 6.19.0-rc8 #61 PREEMPT(non= e) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/= 2014 RIP: 0010:sk_wait_data+0x15/0x190 Code: 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f = 1e fa 41 56 41 55 41 54 49 89 f4 55 48 89 d5 53 48 89 fb <48> 83 ec 30 65 4= 8 8b 05 17 a4 6b 01 48 89 44 24 28 31 c0 65 48 8b RSP: 0018:ffffc90000603ca0 EFLAGS: 00000246 RAX: 0000000000000000 RBX: ffff888102bf0800 RCX: 0000000000000001 RDX: 0000000000000000 RSI: ffffc90000603d18 RDI: ffff888102bf0800 RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000101 R10: 0000000000000000 R11: 0000000000000075 R12: ffffc90000603d18 R13: ffff888102bf0800 R14: ffff888102bf0800 R15: 0000000000000000 FS: 00007f6e38b8c4c0(0000) GS:ffff8881b877e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055aa7bff1680 CR3: 0000000105cbe000 CR4: 00000000000006f0 Call Trace: mptcp_recvmsg+0x547/0x8c0 net/mptcp/protocol.c:2329 inet_recvmsg+0x11f/0x130 net/ipv4/af_inet.c:891 sock_recvmsg+0x94/0xc0 net/socket.c:1100 __sys_recvfrom+0xb2/0x130 net/socket.c:2256 __x64_sys_recvfrom+0x1f/0x30 net/socket.c:2267 do_syscall_64+0x59/0x2d0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x76/0x7e arch/x86/entry/entry_64.S:131 RIP: 0033:0x7f6e386a4a1d Code: 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 8d 05 f1 de 2c 00 41 89 ca = 8b 00 85 c0 75 20 45 31 c9 45 31 c0 b8 2d 00 00 00 0f 05 <48> 3d 00 f0 ff f= f 77 6b f3 c3 66 0f 1f 84 00 00 00 00 00 41 56 41 RSP: 002b:00007ffc3c4bb078 EFLAGS: 00000246 ORIG_RAX: 000000000000002d RAX: ffffffffffffffda RBX: 000000000000861e RCX: 00007f6e386a4a1d RDX: 00000000000003ff RSI: 00007ffc3c4bb150 RDI: 0000000000000004 RBP: 00007ffc3c4bb570 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000103 R11: 0000000000000246 R12: 00005605dbc00be0 R13: 00007ffc3c4bb650 R14: 0000000000000000 R15: 0000000000000000 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, struc= t 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 =3D mptcp_sk(sk); struct sk_buff *skb, *tmp; @@ -2058,6 +2058,8 @@ static int __mptcp_recvmsg_mskq(struct sock *sk, stru= ct msghdr *msg, } =20 mptcp_eat_recv_skb(sk, skb); + } else { + *last =3D skb; } =20 if (copied >=3D len) @@ -2263,6 +2265,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msgh= dr *msg, size_t len, { struct mptcp_sock *msk =3D mptcp_sk(sk); struct scm_timestamping_internal tss; + struct sk_buff *last =3D NULL; int copied =3D 0, cmsg_flags =3D 0; int target; long timeo; @@ -2291,7 +2294,8 @@ static int mptcp_recvmsg(struct sock *sk, struct msgh= dr *msg, size_t len, int err, bytes_read; =20 bytes_read =3D __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 =3D bytes_read; @@ -2343,7 +2347,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msgh= dr *msg, size_t len, =20 pr_debug("block timeout %ld\n", timeo); mptcp_cleanup_rbuf(msk, copied); - err =3D sk_wait_data(sk, &timeo, NULL); + err =3D sk_wait_data(sk, &timeo, last); if (err < 0) { err =3D copied ? : err; goto out_err; --=20 2.34.1