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 B8D1438836A; Thu, 9 Apr 2026 11:45:34 +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=1775735134; cv=none; b=nZnIm1l9ivhrzyx9BjhZBRDf4q8s+KjwWw1H3IJRM3OtgeK4+masd6CxmlYqLtE8zdoplBDOCJ/YesV2Dg+n3rFm6u+injJibpiNmFRDPTiJFMf9ySSrUdqqVLSjgSgNm5aBHzzJ4uPf3t3eFG3BneaN65KxOq/D1uuwUnBktHE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775735134; c=relaxed/simple; bh=50MkiAbVt7I8o9d1BKURD7MtyMbFg2dS4KX3vjddlsA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=JVPV40okyTfcSrpmVT36pr0YV8oXmdl2JGvCU2GUAMt0xzE/mubqg0Bg5kZoDV7HhhzKuVwTxJIFokM8Kso7DSBzQ1r2sCjEpe185na6ChMvqFCydzHGWeaPhhyMX0DGwh8cU4O+Dp8NEbbAP+d42W+UiTV+t0K/79czFb3UTtE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=odAE712+; 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="odAE712+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 524A8C2BC87; Thu, 9 Apr 2026 11:45:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775735134; bh=50MkiAbVt7I8o9d1BKURD7MtyMbFg2dS4KX3vjddlsA=; h=From:To:Cc:Subject:Date:From; b=odAE712+YzJkCWXpMCKqBPvOXky+il3Qs33PFyl2IVDg6LTrtnQ6tYkuZwkOuVKd+ 2Scmrjk4hfE75I7Q844sJjRCNqWiWaV0Sbhu5uBA0Q1feyHdOOxd8MLas9dPOzw4Ge fNIao1iCHakTwUZSM2CNKJP9ve/rRZ77EZAA2BH8B0Q+ryX9GBape+wa1jtRsdT50E xm1quN5u46MQCU4D6yrldaHVgpz41iVuH669Pn7IMOW8o8l0Up1MW/P2Agd67eDAIE /DjTVFl4gQkQt8qoQnUNoBpzSnczr3cyNJUbsJUENufVZdHZdw9mJucdMzxwfGUDJj rCaxT8JbczoxQ== From: "Matthieu Baerts (NGI0)" To: stable@vger.kernel.org, gregkh@linuxfoundation.org, sashal@kernel.org Cc: MPTCP Upstream , Li Xiasong , "Matthieu Baerts (NGI0)" , Jakub Kicinski Subject: [PATCH 6.6.y] mptcp: fix soft lockup in mptcp_recvmsg() Date: Thu, 9 Apr 2026 13:45:26 +0200 Message-ID: <20260409114525.1159899-2-matttbe@kernel.org> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5224; i=matttbe@kernel.org; h=from:subject; bh=a/uxjm+nSJGTdf8zPfmSiLHrAtbKBhqHQHfs5R2JC1I=; b=owGbwMvMwCVWo/Th0Gd3rumMp9WSGDKvTwyLfu6Snm2iJrzEVf2PxLQu3emZQcsvp0wMejDvo 9fRRHvfjlIWBjEuBlkxRRbptsj8mc+reEu8/Cxg5rAygQxh4OIUgIl8c2VkWKguH31NafeTmz+9 j96cdORgWfmv+PMCN1x3PbK/22RX/p3hf/49b42WdQ+zIq88at0rmXVn5eLsnVJdcpKPbPycDHW NmAE= X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 Content-Transfer-Encoding: 8bit From: Li Xiasong commit 5dd8025a49c268ab6b94d978532af3ad341132a7 upstream. 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(none) 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 48 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 ff 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: 8e04ce45a8db ("mptcp: fix MSG_PEEK stream corruption") Signed-off-by: Li Xiasong Reviewed-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260330120335.659027-1-lixiasong1@huawei.com Signed-off-by: Jakub Kicinski [ Conflicts in protocol.c, because commit bc68b0efa1bf ("mptcp: move the whole rx path under msk socket lock protection") and commit d88b2127b242 ("mptcp: add eat_recv_skb helper") (with some dependences) are not in this version. These conflicts were in the context, and not related to this fix. ] Signed-off-by: Matthieu Baerts (NGI0) --- net/mptcp/protocol.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 85ef9042873b..517b9a5b6867 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1960,7 +1960,7 @@ static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk, 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 sk_buff *skb, *tmp; int total_data_len = 0; @@ -1976,6 +1976,7 @@ static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk, /* skip already peeked skbs */ if (total_data_len + data_len <= copied_total) { total_data_len += data_len; + *last = skb; continue; } @@ -2016,6 +2017,8 @@ static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk, WRITE_ONCE(msk->rmem_released, msk->rmem_released + skb->truesize); __skb_unlink(skb, &msk->receive_queue); __kfree_skb(skb); + } else { + *last = skb; } if (copied >= len) @@ -2237,10 +2240,12 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, cmsg_flags = MPTCP_CMSG_INQ; while (copied < len) { + struct sk_buff *last = NULL; int err, bytes_read; bytes_read = __mptcp_recvmsg_mskq(msk, msg, len - copied, flags, - copied, &tss, &cmsg_flags); + copied, &tss, &cmsg_flags, + &last); if (unlikely(bytes_read < 0)) { if (!copied) copied = bytes_read; @@ -2298,7 +2303,7 @@ 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; -- 2.53.0