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 CAF27C352A1 for ; Tue, 6 Dec 2022 17:16:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235486AbiLFRQe (ORCPT ); Tue, 6 Dec 2022 12:16:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51662 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235639AbiLFRQ3 (ORCPT ); Tue, 6 Dec 2022 12:16:29 -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 7259E2188D for ; Tue, 6 Dec 2022 09:16:28 -0800 (PST) Received: by mail-wr1-x436.google.com with SMTP id m14so24445648wrh.7 for ; Tue, 06 Dec 2022 09:16:28 -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=C0xyPzMK8aZT42PU9SFloI5pO/HMq7geQSaF2uDGzpg=; b=peSpwC2anpKoImJ1wUf7retz31009uPQhtJOwag+lnvh+mIiC8kLKJxCO09XJym9hg zC7pIN6u8QQ3BfDkUPUmzBZGzbT6BFj9lZMZOtup85Y1kFS/7fao1SgTTgsgInVV1Kt4 TlqjIoaTXnj3W/Ot88tCOaE/XeOgayt6aNKtTlF+zzLnKlllIHHEW64JKhwZQRq7a6jI 2+sZzjSoqTB35UbP0vlLxoikt9bfWRoBferbuquK4UwjfPU9JhXh0fzTbq0R4k+2a08C X4lNR6lPNVim6I+mAZKYEuNGVONK7BjMuNChW1aO/fU2TclFRjnlJHbnuquADqzvbrPq 8YMA== 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=C0xyPzMK8aZT42PU9SFloI5pO/HMq7geQSaF2uDGzpg=; b=EkLBpoIWZ4KR9XTaS+ttn2Fmy2a2IkJXtzwBs8F71Do1b5+IUMnVKA2zAbeIfXPhDJ 4EqvQjRePjXaA8Wlemyct3CBT6NMnxprU8MAIJEgYOlCvTfeSjLIJUSjLJm+jWtjiPTc DoZGYy/R2JN00XtyA63mrljdTZ8HpV9gWuuOvYLA4+KMMdkxq6FfgGPHbcHEvIM3hN5V dKT5Hm07JDcncFswp6guLF8ldZLFPWLNltUN1LW1ZQcg0kU2FqEmdcfRTN/q9ug8rmti c+SvMJR78apA01M6bL/qU+rlpA4oi+ECylLF5KuSzP3FLuJUhS831XNMOx8WeiMmn2yK 7iAg== X-Gm-Message-State: ANoB5pmtJkyEfjyitTuHCwUhH43moUgp412Ry4+zVNZl5CuPWD4e0Qz8 kFaqSU7Duttwg8nm+bggp5iywjrg0I/3BrFZ X-Google-Smtp-Source: AA0mqf4/OXced4oOf1NhuTbmp/7q9foSAWknfk5H0+xXuKTC/Epv92jA3DhqYmypl1edbFf0pMhL2A== X-Received: by 2002:adf:fb45:0:b0:241:ea14:f22b with SMTP id c5-20020adffb45000000b00241ea14f22bmr37077859wrs.460.1670346986978; Tue, 06 Dec 2022 09:16:26 -0800 (PST) Received: from localhost ([2a00:79e0:9d:4:d775:c942:f0bf:947f]) by smtp.gmail.com with ESMTPSA id h130-20020a1c2188000000b003b4fdbb6319sm25209861wmh.21.2022.12.06.09.16.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Dec 2022 09:16:26 -0800 (PST) From: Jann Horn To: stable@vger.kernel.org Subject: [PATCH stable 4.9,4.14 2/2] mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths Date: Tue, 6 Dec 2022 18:16:03 +0100 Message-Id: <20221206171614.1183048-2-jannh@google.com> X-Mailer: git-send-email 2.39.0.rc0.267.gcb52ba06e7-goog In-Reply-To: <20221206171614.1183048-1-jannh@google.com> References: <20221206171614.1183048-1-jannh@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org commit f268f6cf875f3220afc77bdd0bf1bb136eb54db9 upstream. 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 f67c02010add..7ad88b9e5a65 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1291,13 +1291,20 @@ 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.rc0.267.gcb52ba06e7-goog