From patchwork Mon Dec 6 14:56:26 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 522151 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 270A5C43219 for ; Mon, 6 Dec 2021 15:15:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346003AbhLFPRO (ORCPT ); Mon, 6 Dec 2021 10:17:14 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:35368 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356431AbhLFPPa (ORCPT ); Mon, 6 Dec 2021 10:15:30 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id F230A61327; Mon, 6 Dec 2021 15:12:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 133B0C341C1; Mon, 6 Dec 2021 15:12:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1638803521; bh=NxzRgyFnR3dc6cOCKeXO9Dht1Vb/nVABovmSyUNzP1Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ox4l1F/dYm+nEbqUGNwX6DQy5fx20gzIrCUeEGXfcdf6pUeufuAEkfgDppqcseGJH UfcoZuhM4TeFwGISg5xisAjQJABlEaWfaoi173iYlXSy7bFYJysix7YLFbWfdYWrLf tLdJCR4OX0a1BiM7lWPQJCwxpmo51V3KF/H2d5W8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+e979d3597f48262cb4ee@syzkaller.appspotmail.com, Wen Gu , Tony Lu , "David S. Miller" , Sasha Levin Subject: [PATCH 5.4 22/70] net/smc: Avoid warning of possible recursive locking Date: Mon, 6 Dec 2021 15:56:26 +0100 Message-Id: <20211206145552.688510133@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211206145551.909846023@linuxfoundation.org> References: <20211206145551.909846023@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Wen Gu [ Upstream commit 7a61432dc81375be06b02f0061247d3efbdfce3a ] Possible recursive locking is detected by lockdep when SMC falls back to TCP. The corresponding warnings are as follows: ============================================ WARNING: possible recursive locking detected 5.16.0-rc1+ #18 Tainted: G E -------------------------------------------- wrk/1391 is trying to acquire lock: ffff975246c8e7d8 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0x109/0x250 [smc] but task is already holding lock: ffff975246c8f918 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0xfe/0x250 [smc] other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&ei->socket.wq.wait); lock(&ei->socket.wq.wait); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by wrk/1391: #0: ffff975246040130 (sk_lock-AF_SMC){+.+.}-{0:0}, at: smc_connect+0x43/0x150 [smc] #1: ffff975246c8f918 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0xfe/0x250 [smc] stack backtrace: Call Trace: dump_stack_lvl+0x56/0x7b __lock_acquire+0x951/0x11f0 lock_acquire+0x27a/0x320 ? smc_switch_to_fallback+0x109/0x250 [smc] ? smc_switch_to_fallback+0xfe/0x250 [smc] _raw_spin_lock_irq+0x3b/0x80 ? smc_switch_to_fallback+0x109/0x250 [smc] smc_switch_to_fallback+0x109/0x250 [smc] smc_connect_fallback+0xe/0x30 [smc] __smc_connect+0xcf/0x1090 [smc] ? mark_held_locks+0x61/0x80 ? __local_bh_enable_ip+0x77/0xe0 ? lockdep_hardirqs_on+0xbf/0x130 ? smc_connect+0x12a/0x150 [smc] smc_connect+0x12a/0x150 [smc] __sys_connect+0x8a/0xc0 ? syscall_enter_from_user_mode+0x20/0x70 __x64_sys_connect+0x16/0x20 do_syscall_64+0x34/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae The nested locking in smc_switch_to_fallback() is considered to possibly cause a deadlock because smc_wait->lock and clc_wait->lock are the same type of lock. But actually it is safe so far since there is no other place trying to obtain smc_wait->lock when clc_wait->lock is held. So the patch replaces spin_lock() with spin_lock_nested() to avoid false report by lockdep. Link: https://lkml.org/lkml/2021/11/19/962 Fixes: 2153bd1e3d3d ("Transfer remaining wait queue entries during fallback") Reported-by: syzbot+e979d3597f48262cb4ee@syzkaller.appspotmail.com Signed-off-by: Wen Gu Acked-by: Tony Lu Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/smc/af_smc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index 00d3787387172..fa3b20e5f4608 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -483,7 +483,7 @@ static void smc_switch_to_fallback(struct smc_sock *smc) * to clcsocket->wq during the fallback. */ spin_lock_irqsave(&smc_wait->lock, flags); - spin_lock(&clc_wait->lock); + spin_lock_nested(&clc_wait->lock, SINGLE_DEPTH_NESTING); list_splice_init(&smc_wait->head, &clc_wait->head); spin_unlock(&clc_wait->lock); spin_unlock_irqrestore(&smc_wait->lock, flags);