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 515C626CE32; Mon, 13 Apr 2026 16:11:37 +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=1776096697; cv=none; b=J7giglk7DRroat5kCkz3EdUbyCX7AWSb/kKb2SSFSLHeF8KhQoD3UwVLKCL5Kxrc7yBGE+mweQ1MwF7uDH3lzSVhBP1KwCC7xcGabN32KY0OVWvHeGv5MHR7HegRxIXrrDqlBWuqJFD+AgUJ4VGPSmWKojPlVCRCyq9mA0l+M/U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776096697; c=relaxed/simple; bh=ssNk2we/VRow1CJ72jjh+MosBIgSG9X4p8ODEmxIrGc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HAE1w27EZXGPh32Bi7hbAXHPhX/K73oYUhzRrT9NOo0I5lNKQL3gdwQ/S0PsyZJrg3uO7+ONG81zZs+ww56uiuTnAMerAj91+ya0QHhHbl4MCblnoXTUEn3IHCPlsjhBQtAuWnh49/rOPKW7bZulXI6VPcZ3NyAZG8xWj1IvCnM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=NxDE0NkE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="NxDE0NkE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DD757C2BCAF; Mon, 13 Apr 2026 16:11:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1776096697; bh=ssNk2we/VRow1CJ72jjh+MosBIgSG9X4p8ODEmxIrGc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NxDE0NkEMns0J+kx6pMZcb5cCsT1VUV+kGPMlPqeKaZxLxtN5Gf5QvnrzH1JBLJ0m b3Tc/xkSxjIjP2qyHz/x6nonBbSenslT/qRPdFVq5IE9CNUcEfFnwmk86v8WDQSheV qSeO9fCUOv61iSNs9AH5sgBgSah10Wl3qpnxTWOM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Li Xiasong , "Matthieu Baerts (NGI0)" , Jakub Kicinski Subject: [PATCH 6.12 28/70] mptcp: fix soft lockup in mptcp_recvmsg() Date: Mon, 13 Apr 2026 18:00:23 +0200 Message-ID: <20260413155729.239617101@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260413155728.181580293@linuxfoundation.org> References: <20260413155728.181580293@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ 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) Signed-off-by: Greg Kroah-Hartman --- net/mptcp/protocol.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1997,7 +1997,7 @@ static int __mptcp_recvmsg_mskq(struct m 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; @@ -2013,6 +2013,7 @@ static int __mptcp_recvmsg_mskq(struct m /* skip already peeked skbs */ if (total_data_len + data_len <= copied_total) { total_data_len += data_len; + *last = skb; continue; } @@ -2053,6 +2054,8 @@ static int __mptcp_recvmsg_mskq(struct m 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) @@ -2274,10 +2277,12 @@ static int mptcp_recvmsg(struct sock *sk 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; @@ -2335,7 +2340,7 @@ static int mptcp_recvmsg(struct sock *sk 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;