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 980EAC4332F for ; Mon, 12 Dec 2022 17:32:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229607AbiLLRcu (ORCPT ); Mon, 12 Dec 2022 12:32:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41284 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229536AbiLLRct (ORCPT ); Mon, 12 Dec 2022 12:32:49 -0500 Received: from mail-wr1-x436.google.com (mail-wr1-x436.google.com [IPv6:2a00:1450:4864:20::436]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E25DAEA6 for ; Mon, 12 Dec 2022 09:32:46 -0800 (PST) Received: by mail-wr1-x436.google.com with SMTP id y16so12892326wrm.2 for ; Mon, 12 Dec 2022 09:32:46 -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:to:from:from:to:cc:subject:date:message-id :reply-to; bh=5C9kI8SgZJmSI1TlAclMjxHv7RPCNM7AH9sGx7kYp8U=; b=EakQPkEN3TvI9KhiR4YTQEHuyf6SpMFr+2qwGY1LlgkOt7T6CVSFFEyILQAs2lf11w YH4EnwX40Jey9RaG6PUn7cM/pfiqmKjFvngs2suQOwrbUGwj1HS6+jbSQv9GZi8uuodC LkGeQk/ZzvoXYCkEYB7R/Jk9y4IUUk9nRMxQIWAQNvMYIRV2aZnrlZ7yeRa83MkYC+Ig RBsJTjgoGV2dbo+Latcz4jN+bLGBSW6sio/MvkWCu12MQSVhYteaNSIr98Nu5dGSwlMd 0L50GPtSwYMR5k5RMg7GSwdSVfNGvqX3ML+5Qb9qNwyi4m5lAqf4duxY8xcLwhzvtgFt s6/w== 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:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=5C9kI8SgZJmSI1TlAclMjxHv7RPCNM7AH9sGx7kYp8U=; b=yf9uDutyXMvexHNJL+FtS6rG6xK+RgVCkU2Raw3Lxcz4LrAnIdejn+kk5iIf2hhDos R6x/de3jINoUE2z33fXSMB4nXQZzVKTwKqiXeY6MJ9WYCtMUBBumxLust0YJMTIoknhQ jtaCaReEGx1U/WyJ2lngpOAfhEJF39lt8cWnpg+jvb0VhTaR50WvZ1bEkZMEUEhmQsnO vSZqmMTO5H5bFnQ6yo/J1QyKEzHFWHmf8ev2buGK0KsNluhfUM2jv+B9xyrf/Kor9TQw sU4q+NSDTwNBDmLKvh/KvSv71QUG34TFAJ+9KxJ+EgLofa9bNcHKk1e1TUdIEFBvo2+h 2Dig== X-Gm-Message-State: ANoB5pkr1UR+1ukDWEOq0uHH83Max0TTrEYOucLVCTB+2f6fvs84Z+Ba 6PMsx5ajOiaVTpwnkrSjr236bXK7GznNHiJ2 X-Google-Smtp-Source: AA0mqf4/jDxMMp5JEE3S1OJvZr2LJYp51IIOdrGK67k76aQXZhe42byl5gSga1DWEu0PFzLzFvT5gQ== X-Received: by 2002:a05:6000:256:b0:242:e80:7ce0 with SMTP id m22-20020a056000025600b002420e807ce0mr630510wrz.2.1670866365029; Mon, 12 Dec 2022 09:32:45 -0800 (PST) Received: from localhost ([2a00:79e0:9d:4:d108:797c:2f44:5af6]) by smtp.gmail.com with ESMTPSA id fc18-20020a05600c525200b003cfd64b6be1sm12961964wmb.27.2022.12.12.09.32.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Dec 2022 09:32:44 -0800 (PST) From: Jann Horn To: stable@vger.kernel.org Subject: [PATCH v2 stable 4.19 2/2] mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths Date: Mon, 12 Dec 2022 18:32:36 +0100 Message-Id: <20221212173238.963128-2-jannh@google.com> X-Mailer: git-send-email 2.39.0.rc1.256.g54fd8350bd-goog In-Reply-To: <20221212173238.963128-1-jannh@google.com> References: <20221212173238.963128-1-jannh@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@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. Link: https://lkml.kernel.org/r/20221129154730.2274278-3-jannh@google.com Link: https://lkml.kernel.org/r/20221128180252.1684965-3-jannh@google.com Link: https://lkml.kernel.org/r/20221125213714.4115729-3-jannh@google.com Fixes: f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages") Signed-off-by: Jann Horn Acked-by: David Hildenbrand Reviewed-by: Yang Shi Cc: John Hubbard Cc: Peter Xu Cc: Signed-off-by: Andrew Morton [manual backport: this code was refactored from two copies into a common helper between 5.15 and 6.0; pmd collapse for PTE-mapped THP was only added in 5.4; MMU notifier API changed between 4.19 and 5.4] Signed-off-by: Jann Horn --- mm/khugepaged.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 0f217bb9b534..bddc1a20653d 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1303,13 +1303,20 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) */ if (down_write_trylock(&mm->mmap_sem)) { if (!khugepaged_test_exit(mm)) { - spinlock_t *ptl = pmd_lock(mm, pmd); + spinlock_t *ptl; + unsigned long end = addr + HPAGE_PMD_SIZE; + + mmu_notifier_invalidate_range_start(mm, addr, + end); + ptl = pmd_lock(mm, pmd); /* assume page table is clear */ _pmd = pmdp_collapse_flush(vma, addr, pmd); spin_unlock(ptl); mm_dec_nr_ptes(mm); tlb_remove_table_sync_one(); pte_free(mm, pmd_pgtable(_pmd)); + mmu_notifier_invalidate_range_end(mm, addr, + end); } up_write(&mm->mmap_sem); } -- 2.39.0.rc1.256.g54fd8350bd-goog