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=-3.8 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 autolearn=no 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 6F084C54FCB for ; Tue, 21 Apr 2020 01:14:20 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2862E2070B for ; Tue, 21 Apr 2020 01:14:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="FwoMTyd1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2862E2070B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CD0478E0013; Mon, 20 Apr 2020 21:14:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C592F8E0003; Mon, 20 Apr 2020 21:14:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A327C8E0013; Mon, 20 Apr 2020 21:14:19 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 8CA948E0003 for ; Mon, 20 Apr 2020 21:14:19 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 518E1181AEF23 for ; Tue, 21 Apr 2020 01:14:19 +0000 (UTC) X-FDA: 76730091438.25.knife63_5fe59fc9d620d X-HE-Tag: knife63_5fe59fc9d620d X-Filterd-Recvd-Size: 4311 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf49.hostedemail.com (Postfix) with ESMTP for ; Tue, 21 Apr 2020 01:14:18 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 F40A2214AF; Tue, 21 Apr 2020 01:14:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587431658; bh=GxrDCTBBZwdqEArAkp6Nrim0SqKgc8oqr3PeojTYHcI=; h=Date:From:To:Subject:In-Reply-To:From; b=FwoMTyd18KjAuaM+9z/y7zMi7OGkyWJ5AzmJaGlUxdirEwvLX0vSi3MB0PrxGgiQJ HfQZ2NQg/qmBXVkvvWrcJR9uFaaCaW0kU7mfOXKCb7Lms+UqhFwzJobuPMX7osL9WM QEZV/BSDbuFF8LExcws6nnrfg2TyZiENvnr9Khk8= Date: Mon, 20 Apr 2020 18:14:17 -0700 From: Andrew Morton To: aarcange@redhat.com, akpm@linux-foundation.org, hughd@google.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, yang.shi@linux.alibaba.com Subject: [patch 13/15] mm: shmem: disable interrupt when acquiring info->lock in userfaultfd_copy path Message-ID: <20200421011417.dQjjscoWH%akpm@linux-foundation.org> In-Reply-To: <20200420181310.c18b3c0aa4dc5b3e5ec1be10@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Yang Shi Subject: mm: shmem: disable interrupt when acquiring info->lock in userfaultfd_copy path 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. Link: http://lkml.kernel.org/r/1587061357-122619-1-git-send-email-yang.shi@linux.alibaba.com Fixes: 4c27fe4c4c84 ("userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support") Signed-off-by: Yang Shi Reported-by: syzbot+e27980339d305f2dbfd9@syzkaller.appspotmail.com Tested-by: syzbot+e27980339d305f2dbfd9@syzkaller.appspotmail.com Acked-by: Hugh Dickins Cc: Andrea Arcangeli Signed-off-by: Andrew Morton --- mm/shmem.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/shmem.c~mm-shmem-disable-interrupt-when-acquiring-info-lock-in-userfaultfd_copy-path +++ a/mm/shmem.c @@ -2402,11 +2402,11 @@ 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); _