From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08870C47258 for ; Fri, 1 May 2020 13:54:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DBDC424956 for ; Fri, 1 May 2020 13:54:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588341269; bh=kkYlaCzeAPTBAZUCrEwg/VKcVhWrWErN3+we1EYbLZU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=TnrtsEcCuoGNDxQH6PRkzoMNNIbunsKic7cBf4ZeKwnrHOKkg371n6ZgFvAmX4CLp Ay31BgYshzn5Z35M0DMUTYhUzP8i+cjqwe4if8esiG7rWZq7JfsIpuh9Vt0o0BVaOd Pw0CUy7t4leqkRAh2DpQs+k7yNfgPt2HieIojru8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730743AbgEANfP (ORCPT ); Fri, 1 May 2020 09:35:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:33418 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730679AbgEANfK (ORCPT ); Fri, 1 May 2020 09:35:10 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id ED19C24953; Fri, 1 May 2020 13:35:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588340109; bh=kkYlaCzeAPTBAZUCrEwg/VKcVhWrWErN3+we1EYbLZU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bvto7ViGFlBawLGKeURGIMud73vw+l15DuvoVd74EUb3q3dcsolMhGgmW/jXyWnXR xehWmeM6AzFA5Ojti6s1O79p1MkxuG4q13cJQdxxHNqt1GRDFY99dScn5XgYCyuDY5 cshjvPnoW+KpDS0FOZWgT1pC6/xc9pBYlnUMELkI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+e27980339d305f2dbfd9@syzkaller.appspotmail.com, Yang Shi , Andrew Morton , Hugh Dickins , Andrea Arcangeli , Linus Torvalds Subject: [PATCH 4.14 097/117] mm: shmem: disable interrupt when acquiring info->lock in userfaultfd_copy path Date: Fri, 1 May 2020 15:22:13 +0200 Message-Id: <20200501131556.737155505@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200501131544.291247695@linuxfoundation.org> References: <20200501131544.291247695@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yang Shi commit 94b7cc01da5a3cc4f3da5e0ff492ef008bb555d6 upstream. Syzbot reported the below lockdep splat: WARNING: possible irq lock inversion dependency detected 5.6.0-rc7-syzkaller #0 Not tainted -------------------------------------------------------- syz-executor.0/10317 just changed the state of lock: ffff888021d16568 (&(&info->lock)->rlock){+.+.}, at: spin_lock include/linux/spinlock.h:338 [inline] ffff888021d16568 (&(&info->lock)->rlock){+.+.}, at: shmem_mfill_atomic_pte+0x1012/0x21c0 mm/shmem.c:2407 but this lock was taken by another, SOFTIRQ-safe lock in the past: (&(&xa->xa_lock)->rlock#5){..-.} and interrupts could create inverse lock ordering between them. other info that might help us debug this: Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&(&info->lock)->rlock); local_irq_disable(); lock(&(&xa->xa_lock)->rlock#5); lock(&(&info->lock)->rlock); lock(&(&xa->xa_lock)->rlock#5); *** DEADLOCK *** The full report is quite lengthy, please see: https://lore.kernel.org/linux-mm/alpine.LSU.2.11.2004152007370.13597@eggly.anvils/T/#m813b412c5f78e25ca8c6c7734886ed4de43f241d It is because CPU 0 held info->lock with IRQ enabled in userfaultfd_copy path, then CPU 1 is splitting a THP which held xa_lock and info->lock in IRQ disabled context at the same time. If softirq comes in to acquire xa_lock, the deadlock would be triggered. The fix is to acquire/release info->lock with *_irq version instead of plain spin_{lock,unlock} to make it softirq safe. Fixes: 4c27fe4c4c84 ("userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support") Reported-by: syzbot+e27980339d305f2dbfd9@syzkaller.appspotmail.com Signed-off-by: Yang Shi Signed-off-by: Andrew Morton Tested-by: syzbot+e27980339d305f2dbfd9@syzkaller.appspotmail.com Acked-by: Hugh Dickins Cc: Andrea Arcangeli Link: http://lkml.kernel.org/r/1587061357-122619-1-git-send-email-yang.shi@linux.alibaba.com Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/shmem.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2330,11 +2330,11 @@ static int shmem_mfill_atomic_pte(struct lru_cache_add_anon(page); - spin_lock(&info->lock); + spin_lock_irq(&info->lock); info->alloced++; inode->i_blocks += BLOCKS_PER_PAGE; shmem_recalc_inode(inode); - spin_unlock(&info->lock); + spin_unlock_irq(&info->lock); inc_mm_counter(dst_mm, mm_counter_file(page)); page_add_file_rmap(page, false);