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 B6E06C46467 for ; Mon, 16 Jan 2023 16:54:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233851AbjAPQyT (ORCPT ); Mon, 16 Jan 2023 11:54:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234001AbjAPQxK (ORCPT ); Mon, 16 Jan 2023 11:53:10 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 56B584C6DF for ; Mon, 16 Jan 2023 08:37:51 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 52B25B80DC7 for ; Mon, 16 Jan 2023 16:37:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9455C433EF; Mon, 16 Jan 2023 16:37:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1673887069; bh=ceUhaMuaFt0AaD9At5cl0zzqnfnvIA5TB1n19OkATyQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PDFbQ0veAdMXgX8IrPqLn0dFFlEnQchbrc6jrkQMdpXh4qozZh49ZflSE6owHl7B7 vV/Ka5VPPac6f83Q88Sgesju+k+wfvxxTty4z6cFPTsbehfv9GMxVd20d+UIp6e7++ RQ8rAxQeUZk1DngxZg13sm/RC2RN7WCjzX8QnH/A= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jann Horn , David Hildenbrand , Yang Shi , John Hubbard , Peter Xu , Andrew Morton Subject: [PATCH 4.19 002/521] mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths Date: Mon, 16 Jan 2023 16:44:24 +0100 Message-Id: <20230116154847.353372882@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230116154847.246743274@linuxfoundation.org> References: <20230116154847.246743274@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jann Horn 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 Signed-off-by: Greg Kroah-Hartman --- mm/khugepaged.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1303,13 +1303,20 @@ static void retract_page_tables(struct a */ 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); }