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 DDFD7C4332F for ; Mon, 21 Nov 2022 18:16:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230411AbiKUSQ6 (ORCPT ); Mon, 21 Nov 2022 13:16:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60466 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230390AbiKUSQr (ORCPT ); Mon, 21 Nov 2022 13:16:47 -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 AB084C696D for ; Mon, 21 Nov 2022 10:16:45 -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 6331DB80D34 for ; Mon, 21 Nov 2022 18:16:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D0BFC433B5; Mon, 21 Nov 2022 18:16:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669054603; bh=9v6sSKGZm6rKD4Rjxu2zJKwI5WScIH+ealnL74DQ/PU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RxHd4eI4wCHTrAFjdgfLlEbo0iAhNvzvP1Jp76pVEu1Nb59RAHd+oJXngb1stKQsT NHacu+O4e5kN1pxdGJLzY7C2vaai0Z1+vfPbTeR0DqLzJtkcZdCtG5UcFonCCRvzog YubtUy6hFEDzWQjPQ2EyduH93GNfsJTabu9d1OeqEbkDXO/7/nI/RNdDyZXb2S+Arz InEyoXRf2soN2T4kPJIzkZLDjys5ugwyAynDpR1Dx5ieJlVlyVM2cutG4Z93JOKkYA Ddn0DQmOSLnq/Y0E+0YGwEB2CaERWRG7ikHbT5vBEuPhdf2jHSnfc62NI+KmY7uC9C SwMGCOgfRP16g== Date: Mon, 21 Nov 2022 18:16:37 +0000 From: Will Deacon To: Liu Shixin Cc: Catalin Marinas , Denys Vlasenko , Kefeng Wang , Anshuman Khandual , David Hildenbrand , Rafael Aquini , Pasha Tatashin , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/2] arm64/mm: fix incorrect file_map_count for invalid pmd/pud Message-ID: <20221121181636.GD7645@willie-the-truck> References: <20221117075602.2904324-1-liushixin2@huawei.com> <20221117075602.2904324-3-liushixin2@huawei.com> <20221118143414.GG4046@willie-the-truck> <10cecbdf-eb06-873d-6b79-bfdb3197d2ec@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <10cecbdf-eb06-873d-6b79-bfdb3197d2ec@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 21, 2022 at 11:15:49AM +0800, Liu Shixin wrote: > 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(). I can believe they don't get exposed to userspace at all, but exposing only as non-executable doesn't sound right. So I would have thought that either pud_user_accessible_page() would always return false or it would need to check for the executable case too. Will