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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CBC3BC433FE for ; Mon, 28 Nov 2022 18:19:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234222AbiK1STk (ORCPT ); Mon, 28 Nov 2022 13:19:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55666 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234201AbiK1SSz (ORCPT ); Mon, 28 Nov 2022 13:18:55 -0500 Received: from mail-wm1-x329.google.com (mail-wm1-x329.google.com [IPv6:2a00:1450:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 82933391CC for ; Mon, 28 Nov 2022 10:03:11 -0800 (PST) Received: by mail-wm1-x329.google.com with SMTP id 5so9111604wmo.1 for ; Mon, 28 Nov 2022 10:03:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=l98v59BwmjV3ozOfAPw93XrEkUrol6K2zteQO/pxMQA=; b=e/bGIA0HwGB+g6h3LY4eVczqCQQA7q3lac86AA8ayrG5RmwDmE42BKfG03HoYIQKsz fMIN5YuLApIg7+jeOJkwev91+mwmAodAoBnqKNmf+ZyiCiDkOu2GYqHqzKzhbJWp/ecI vWsg6LX5RDFYedCD530UHz52LBU5F7BC2+HnuTEORVeZrSQlOPbK4fD7O+EJmC+ChSqT 4/QrQNGQYxmjFVHe4CjMFUxzDdcOEnJOVqPakZboLMtfqHUntjEYD8GQnRWIeBPl84lH 7h9OmgR2dU+cq7dQy/wrZmcmqRNiPwgNox6e/naAqPQyFZei0ecGmQ4QHiMSLPBUWKVm BCUw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=l98v59BwmjV3ozOfAPw93XrEkUrol6K2zteQO/pxMQA=; b=GDyfVLrVqxvFqEOrZfFzBGo4M0lvRRcdLqeyHLhQoIxKXFOAiHaBTRXu5u5zZHyOyi LHnILqOEhP/MtnNQRCN+kb+KY7MQkG8rT42MhjFGSi0hRpiVrBNXJ+M+4SZV+3QwiOfk M0DyAkBTPxed+hFPEeVXOAoHqzpier1xldf6YhneNvL6heDkiV72vhHSsKSeaePUcW9J z9P2sqp7PocFtIZCIH6QrZyaXWUy42wBlXELWe4yrdqJmqkkVR4aacTO6epuT1y8uE6j hvZEYnllbKrxWxePNrJnzuO/cuwkEqeQSnu5icSQSbsi7Sm0mo+uC68uzt6UW0Esiqhk RaIw== X-Gm-Message-State: ANoB5pmrvU8l5lzUJzfelhoV5qH/1rxFVQHJIY1TH226oVC2ZcAdn4HU x3PIj/Cu+39U6rS7nMJQyVhL3g== X-Google-Smtp-Source: AA0mqf5bPnlo2nRCz9Eyg7DCrG+Pr9DR0sbrCKNNE0RnhBm/HPey1JfsWRdDN/GOXPZxYrMjEe4RKA== X-Received: by 2002:a05:600c:4fd0:b0:3cf:70a0:f689 with SMTP id o16-20020a05600c4fd000b003cf70a0f689mr43238540wmq.161.1669658589915; Mon, 28 Nov 2022 10:03:09 -0800 (PST) Received: from localhost ([2a00:79e0:9d:4:f4d1:b340:8675:e840]) by smtp.gmail.com with ESMTPSA id d8-20020a5d6dc8000000b002415dd45320sm11359859wrz.112.2022.11.28.10.03.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Nov 2022 10:03:09 -0800 (PST) From: Jann Horn To: security@kernel.org, Andrew Morton Cc: Yang Shi , David Hildenbrand , Peter Xu , John Hubbard , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v4 3/3] mm/khugepaged: Invoke MMU notifiers in shmem/file collapse paths Date: Mon, 28 Nov 2022 19:02:52 +0100 Message-Id: <20221128180252.1684965-3-jannh@google.com> X-Mailer: git-send-email 2.38.1.584.g0f3c55d4c2-goog In-Reply-To: <20221128180252.1684965-1-jannh@google.com> References: <20221128180252.1684965-1-jannh@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Any codepath that zaps page table entries must invoke MMU notifiers to ensure that secondary MMUs (like KVM) don't keep accessing pages which aren't mapped anymore. Secondary MMUs don't hold their own references to pages that are mirrored over, so failing to notify them can lead to page use-after-free. I'm marking this as addressing an issue introduced in commit f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages"), but most of the security impact of this only came in commit 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP"), which actually omitted flushes for the removal of present PTEs, not just for the removal of empty page tables. Cc: stable@kernel.org Fixes: f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages") Signed-off-by: Jann Horn --- v4: no changes mm/khugepaged.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index c3d3ce596bff7..49eb4b4981d88 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1404,6 +1404,7 @@ static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *v unsigned long addr, pmd_t *pmdp) { pmd_t pmd; + struct mmu_notifier_range range; mmap_assert_write_locked(mm); if (vma->vm_file) @@ -1415,8 +1416,12 @@ static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *v if (vma->anon_vma) lockdep_assert_held_write(&vma->anon_vma->root->rwsem); + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, addr, + addr + HPAGE_PMD_SIZE); + mmu_notifier_invalidate_range_start(&range); pmd = pmdp_collapse_flush(vma, addr, pmdp); tlb_remove_table_sync_one(); + mmu_notifier_invalidate_range_end(&range); mm_dec_nr_ptes(mm); page_table_check_pte_clear_range(mm, addr, pmd); pte_free(mm, pmd_pgtable(pmd)); -- 2.38.1.584.g0f3c55d4c2-goog