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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 F111BECDE43 for ; Fri, 19 Oct 2018 16:05:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C09EF20869 for ; Fri, 19 Oct 2018 16:05:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C09EF20869 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727857AbeJTALy (ORCPT ); Fri, 19 Oct 2018 20:11:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48426 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727740AbeJTALe (ORCPT ); Fri, 19 Oct 2018 20:11:34 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1AF9F32B660; Fri, 19 Oct 2018 16:04:51 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-124-217.rdu2.redhat.com [10.10.124.217]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6220165314; Fri, 19 Oct 2018 16:04:50 +0000 (UTC) From: jglisse@redhat.com To: linux-mm@kvack.org Cc: Andrew Morton , linux-kernel@vger.kernel.org, Ralph Campbell , stable@vger.kernel.org Subject: [PATCH 3/6] mm/hmm: fix race between hmm_mirror_unregister() and mmu_notifier callback Date: Fri, 19 Oct 2018 12:04:39 -0400 Message-Id: <20181019160442.18723-4-jglisse@redhat.com> In-Reply-To: <20181019160442.18723-1-jglisse@redhat.com> References: <20181019160442.18723-1-jglisse@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 19 Oct 2018 16:04:51 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ralph Campbell In hmm_mirror_unregister(), mm->hmm is set to NULL and then mmu_notifier_unregister_no_release() is called. That creates a small window where mmu_notifier can call mmu_notifier_ops with mm->hmm equal to NULL. Fix this by first unregistering mmu notifier callbacks and then setting mm->hmm to NULL. Similarly in hmm_register(), set mm->hmm before registering mmu_notifier callbacks so callback functions always see mm->hmm set. Signed-off-by: Ralph Campbell Reviewed-by: John Hubbard Reviewed-by: Jérôme Glisse Reviewed-by: Balbir Singh Cc: Andrew Morton Cc: stable@vger.kernel.org --- mm/hmm.c | 36 +++++++++++++++++++++--------------- 1 file changed, 21 insertions(+), 15 deletions(-) diff --git a/mm/hmm.c b/mm/hmm.c index 9a068a1da487..a16678d08127 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -91,16 +91,6 @@ static struct hmm *hmm_register(struct mm_struct *mm) spin_lock_init(&hmm->lock); hmm->mm = mm; - /* - * We should only get here if hold the mmap_sem in write mode ie on - * registration of first mirror through hmm_mirror_register() - */ - hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops; - if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) { - kfree(hmm); - return NULL; - } - spin_lock(&mm->page_table_lock); if (!mm->hmm) mm->hmm = hmm; @@ -108,12 +98,27 @@ static struct hmm *hmm_register(struct mm_struct *mm) cleanup = true; spin_unlock(&mm->page_table_lock); - if (cleanup) { - mmu_notifier_unregister(&hmm->mmu_notifier, mm); - kfree(hmm); - } + if (cleanup) + goto error; + + /* + * We should only get here if hold the mmap_sem in write mode ie on + * registration of first mirror through hmm_mirror_register() + */ + hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops; + if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) + goto error_mm; return mm->hmm; + +error_mm: + spin_lock(&mm->page_table_lock); + if (mm->hmm == hmm) + mm->hmm = NULL; + spin_unlock(&mm->page_table_lock); +error: + kfree(hmm); + return NULL; } void hmm_mm_destroy(struct mm_struct *mm) @@ -278,12 +283,13 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror) if (!should_unregister || mm == NULL) return; + mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm); + spin_lock(&mm->page_table_lock); if (mm->hmm == hmm) mm->hmm = NULL; spin_unlock(&mm->page_table_lock); - mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm); kfree(hmm); } EXPORT_SYMBOL(hmm_mirror_unregister); -- 2.17.2