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 45611C4332F for ; Mon, 12 Dec 2022 17:32:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232016AbiLLRcz (ORCPT ); Mon, 12 Dec 2022 12:32:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41344 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232253AbiLLRcx (ORCPT ); Mon, 12 Dec 2022 12:32:53 -0500 Received: from mail-wr1-x42a.google.com (mail-wr1-x42a.google.com [IPv6:2a00:1450:4864:20::42a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C5B7E0F for ; Mon, 12 Dec 2022 09:32:49 -0800 (PST) Received: by mail-wr1-x42a.google.com with SMTP id h16so3921540wrz.12 for ; Mon, 12 Dec 2022 09:32:49 -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=cnCEuIxgtLh0uks0WZG9h0Vph+pJpJv+4KkiXuwg67w=; b=TR5UXdOKLkuQUVVWnbe/qZ7Vmpi9KYcMWhq/UJYZYIbf6W/SCJ57q1dHc4VqpAdtYX t5ysyfOc4uU8dAhO5fEkCYADRnu+ozgi1GGopO8T4Fp/gz5Gi5u0vkFryFbzt/fyzcBH +434ZYhxIIz6hVQuGP58ZJiNxzHFN7mPkZVG3Jtc1EKdWZFyLpQBsUiEyJtLo8q/G80S wfwt/FUoyCaetRiKUGV3WpLrDPf3Anr5ymxSPjPNxMDiiPJ5+vXOvb69EqPEbGYXLG+/ adw9io1NpLpNDc6KYDEheqxrbUh1TuuuKxleFOFXZPq3hFe4Ct3lneeuPV2vhV2ZM6a/ DQ2Q== 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=cnCEuIxgtLh0uks0WZG9h0Vph+pJpJv+4KkiXuwg67w=; b=ADSJoOcAaf2AzTtTHXwpxXF+pXD/JIhmpRA1iiH5o9dPQJBv70cPDEq0cz6UESXoCm 6tyRxSVxVdVzzELWsex9sQIkhntrnAiggShI5dNoQV8GCEJyRlTvKjWMEJXqVskK37SM BR7ixaVT4LeQneE9I+NyoT3XO8jD2+g90aGcXEzYyh2FuOPZwO70fymjQQ2+aHTScMsS 3u6rteMEBZhgF0Q6dT6WO3kt8p+JCQkAnovkNe4RDG9soSe0f+u7LNY0dA+f//QAmvxJ PYdCe8V1Ghg7q1/gRTUXWCxHjC1tJUdyz/IaEE85A/jWI+s82XycB96dzuhnr6lQEwvT sP1g== X-Gm-Message-State: ANoB5pkOugKLrEZUpHg0KpHcsBwyL2wWXN946Q7x8UiHp3s61lfBgF78 hN8MKUPVU7JPv+0I5I1fzqmei/7yLYjej/NO X-Google-Smtp-Source: AA0mqf5g6gScQrqary+MHQqOSQR6KtGeJzuLTaGVn2T9Fp4bektud6duW55a5nk5WOLDbCxjebhSEg== X-Received: by 2002:a5d:5f04:0:b0:24b:b245:9f06 with SMTP id cl4-20020a5d5f04000000b0024bb2459f06mr738256wrb.1.1670866367652; Mon, 12 Dec 2022 09:32:47 -0800 (PST) Received: from localhost ([2a00:79e0:9d:4:d108:797c:2f44:5af6]) by smtp.gmail.com with ESMTPSA id z17-20020adfdf91000000b00241d544c9b1sm11041360wrl.90.2022.12.12.09.32.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Dec 2022 09:32:46 -0800 (PST) From: Jann Horn To: stable@vger.kernel.org Subject: [PATCH v2 stable 4.9,4.14 2/2] mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths Date: Mon, 12 Dec 2022 18:32:38 +0100 Message-Id: <20221212173238.963128-4-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 7825f3af5c6d..a85e4dd6cbf1 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1304,13 +1304,20 @@ 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); atomic_long_dec(&mm->nr_ptes); 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