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 21719C4332F for ; Mon, 21 Nov 2022 03:16:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229833AbiKUDQC (ORCPT ); Sun, 20 Nov 2022 22:16:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229498AbiKUDQA (ORCPT ); Sun, 20 Nov 2022 22:16:00 -0500 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6DFF317FE for ; Sun, 20 Nov 2022 19:15:57 -0800 (PST) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4NFsrp2QnvzFqRk; Mon, 21 Nov 2022 11:12:42 +0800 (CST) Received: from dggpemm100009.china.huawei.com (7.185.36.113) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 21 Nov 2022 11:15:50 +0800 Received: from [10.174.179.24] (10.174.179.24) by dggpemm100009.china.huawei.com (7.185.36.113) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 21 Nov 2022 11:15:49 +0800 Subject: Re: [PATCH v2 2/2] arm64/mm: fix incorrect file_map_count for invalid pmd/pud To: Will Deacon References: <20221117075602.2904324-1-liushixin2@huawei.com> <20221117075602.2904324-3-liushixin2@huawei.com> <20221118143414.GG4046@willie-the-truck> CC: Catalin Marinas , Denys Vlasenko , Kefeng Wang , "Anshuman Khandual" , David Hildenbrand , Rafael Aquini , Pasha Tatashin , , From: Liu Shixin Message-ID: <10cecbdf-eb06-873d-6b79-bfdb3197d2ec@huawei.com> Date: Mon, 21 Nov 2022 11:15:49 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20221118143414.GG4046@willie-the-truck> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.24] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm100009.china.huawei.com (7.185.36.113) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/11/18 22:34, Will Deacon wrote: > On Thu, Nov 17, 2022 at 03:56:02PM +0800, Liu Shixin wrote: >> The page table check trigger BUG_ON() unexpectedly when split hugepage: >> >> ------------[ cut here ]------------ >> kernel BUG at mm/page_table_check.c:119! >> Internal error: Oops - BUG: 00000000f2000800 [#1] SMP >> Dumping ftrace buffer: >> (ftrace buffer empty) >> Modules linked in: >> CPU: 7 PID: 210 Comm: transhuge-stres Not tainted 6.1.0-rc3+ #748 >> Hardware name: linux,dummy-virt (DT) >> pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) >> pc : page_table_check_set.isra.0+0x398/0x468 >> lr : page_table_check_set.isra.0+0x1c0/0x468 >> [...] >> Call trace: >> page_table_check_set.isra.0+0x398/0x468 >> __page_table_check_pte_set+0x160/0x1c0 >> __split_huge_pmd_locked+0x900/0x1648 >> __split_huge_pmd+0x28c/0x3b8 >> unmap_page_range+0x428/0x858 >> unmap_single_vma+0xf4/0x1c8 >> zap_page_range+0x2b0/0x410 >> madvise_vma_behavior+0xc44/0xe78 >> do_madvise+0x280/0x698 >> __arm64_sys_madvise+0x90/0xe8 >> invoke_syscall.constprop.0+0xdc/0x1d8 >> do_el0_svc+0xf4/0x3f8 >> el0_svc+0x58/0x120 >> el0t_64_sync_handler+0xb8/0xc0 >> el0t_64_sync+0x19c/0x1a0 >> [...] >> >> On arm64, pmd_leaf() will return true even if the pmd is invalid due to >> pmd_present_invalid() check. So in pmdp_invalidate() the file_map_count >> will not only decrease once but also increase once. Then in set_pte_at(), >> the file_map_count increase again, and so trigger BUG_ON() unexpectedly. >> >> Fix this problem by adding pmd_valid() in pmd_user_accessible_page(). >> Moreover, add pud_valid() for pud_user_accessible_page() too. >> >> Fixes: 42b2547137f5 ("arm64/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK") >> Reported-by: Denys Vlasenko >> Signed-off-by: Liu Shixin >> Acked-by: Pasha Tatashin >> --- >> arch/arm64/include/asm/pgtable.h | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h >> index edf6625ce965..3bc64199aa2e 100644 >> --- a/arch/arm64/include/asm/pgtable.h >> +++ b/arch/arm64/include/asm/pgtable.h >> @@ -863,12 +863,12 @@ static inline bool pte_user_accessible_page(pte_t pte) >> >> static inline bool pmd_user_accessible_page(pmd_t pmd) >> { >> - return pmd_leaf(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd)); >> + return pmd_valid(pmd) && pmd_leaf(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd)); > Hmm, doesn't this have a funny interaction with PROT_NONE where the pmd is > invalid but present? If you don't care about PROT_NONE, then you could just > do: > > pmd_valid(pmd) && !pmd_table(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd)) > > but if you do care then you could do: > > pmd_leaf(pmd) && !pmd_present_invalid(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd)) I prefer the latter. I will fix and resend later. >> static inline bool pud_user_accessible_page(pud_t pud) >> { >> - return pud_leaf(pud) && pud_user(pud); >> + return pud_valid(pud) && pud_leaf(pud) && pud_user(pud); > Not caused by this patch, but why don't we have something like a > pud_user_exec() check here like we do for the pte and pmd levels? As far as I know, there is no user use the user executable pud on arm64, so didn't define pud_user_exec(). Thanks, > > Will > . >