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=unavailable 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 13ECFC47253 for ; Fri, 1 May 2020 13:53:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E80D5205C9 for ; Fri, 1 May 2020 13:53:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588341184; bh=tU8TJhxBIWcjE1Am1/vlBCvgrjTH7SCZbgZ7JE4Qicw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=XHZV+Y++bgJV0ixsSYHL5z0qR6CUSH20BhPrQ5ft0iH5g7IxDUYIt6fBo7Ca1LBXA hJ8jQv01/PxVUjGMPp5WVxKzvizn2AmHLD66JP1bn2cjcPojgDWpcClrDHluf5h4bG UTT3L7HXueba9dnMmwiDJS2CAUOPh01GDGLkdsiQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730176AbgEANgw (ORCPT ); Fri, 1 May 2020 09:36:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:35508 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730902AbgEANgv (ORCPT ); Fri, 1 May 2020 09:36:51 -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 E240324953; Fri, 1 May 2020 13:36:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588340210; bh=tU8TJhxBIWcjE1Am1/vlBCvgrjTH7SCZbgZ7JE4Qicw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=s6+aJyfNSzN0zAlBMG4e+mpxV/FIXW1hMmFPC02Qy+5CuPWYFd5iAeuBc+lJxIkLF 2d3deSTjJza4AeR3s7U5yEag28XdM/lYxSfjmpIH0R6ZU2C8aXMB7nNmJ3ASYjp99P XSjZdmUANVCBBB6ttlmhqOX8iflJ5xBFyUkt+muU= 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 4.19 25/46] mm: shmem: disable interrupt when acquiring info->lock in userfaultfd_copy path Date: Fri, 1 May 2020 15:22:50 +0200 Message-Id: <20200501131507.682072631@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200501131457.023036302@linuxfoundation.org> References: <20200501131457.023036302@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@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 @@ -2350,11 +2350,11 @@ 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);