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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2D9BECAAA3 for ; Fri, 26 Aug 2022 16:04:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0D108940008; Fri, 26 Aug 2022 12:04:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 08067940007; Fri, 26 Aug 2022 12:04:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E8997940008; Fri, 26 Aug 2022 12:04:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id DAAFD940007 for ; Fri, 26 Aug 2022 12:04:35 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id B42171A0EEE for ; Fri, 26 Aug 2022 16:04:35 +0000 (UTC) X-FDA: 79842216510.10.D9AD157 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf09.hostedemail.com (Postfix) with ESMTP id 2C32F140044 for ; Fri, 26 Aug 2022 16:04:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1661529873; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=obYa+npn1GLmAkgYbBxpj4Xt3ZyWQyXIOu4icthPymg=; b=FPvAfMuFNWTXzK/6saYcIGKkYXTqlNgrthg95JZSi90ijgNJJxiNQqAzTxCjdQ5lGmO9Ld y9owbQGAeKN0tJezcL6CQSwAxMatt1XbVjRiK8ROAaPLwWjAEr1XATpTrR2T3LVKOB2jqS Op8X+Pk91NQyPPWY1+fdWU+ISEQ00wg= Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-88-X-djRIdBN1qcTVq6ToEqRw-1; Fri, 26 Aug 2022 12:04:32 -0400 X-MC-Unique: X-djRIdBN1qcTVq6ToEqRw-1 Received: by mail-qk1-f197.google.com with SMTP id bi16-20020a05620a319000b006bc2334be53so1581945qkb.14 for ; Fri, 26 Aug 2022 09:04:32 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc; bh=obYa+npn1GLmAkgYbBxpj4Xt3ZyWQyXIOu4icthPymg=; b=bsD1+UzTvPngd7TtPY/5GIFqpTOF8YewoTlq8/RkztPPt/CEEx1WN2+yCvUtJtGJB+ kSJqeiOddbCHQOQRFhjQDqln4gkxmJ6UjZYyhCo1KPa9bqmDxh7pH3Rko7Scf3wy5GCX YQp/y8Mk4PfW0wuKHexfY4Qe+WNjwxHIMPmyDdnqyRhTPf9T1dCE58GW6s13WWDx7SKI K7ZuWmVu7Z4Ei+3WJ1X7B+spVV+cl6e34IFtJvXkfboT4iRk37m2hqfeAQZC9sgxpf98 UYXlErXD8Y5VOqIC7oGYrRN/JwjZln/kAIjhZTXUZzvdNctkgg97QzowXXZLsFcjlyq1 kX7w== X-Gm-Message-State: ACgBeo0jlejC39ZCBfWZ1kg0EbJoLXpKQRalgyDmctolA8X04HdO6Ml4 iw8F5pK+1f0PXDCNcdzQzbYTSGxJ5dFkGwfNb33Gmc0c+ntlc+ZSV6zP16NghrOj4sHJHltz49K igwPXTUQo+xk= X-Received: by 2002:a05:620a:31a7:b0:6bc:138:2828 with SMTP id bi39-20020a05620a31a700b006bc01382828mr257534qkb.733.1661529870393; Fri, 26 Aug 2022 09:04:30 -0700 (PDT) X-Google-Smtp-Source: AA6agR5Rf7dOoH2Nl+vrOLRrnLwbhfetodlfuNtPx0kmDcFjxm+hII8W/X98LxoEHwELOlqKLVbq0w== X-Received: by 2002:a05:620a:31a7:b0:6bc:138:2828 with SMTP id bi39-20020a05620a31a700b006bc01382828mr257509qkb.733.1661529870087; Fri, 26 Aug 2022 09:04:30 -0700 (PDT) Received: from xz-m1.local (bras-base-aurron9127w-grc-35-70-27-3-10.dsl.bell.ca. [70.27.3.10]) by smtp.gmail.com with ESMTPSA id bp17-20020a05620a459100b006b9a24dc9d7sm42297qkb.7.2022.08.26.09.04.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Aug 2022 09:04:29 -0700 (PDT) Date: Fri, 26 Aug 2022 12:04:27 -0400 From: Peter Xu To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Huang Ying , stable@vger.kernel.org, Yu Zhao Subject: Re: [PATCH] mm/mprotect: Only reference swap pfn page if type match Message-ID: References: <20220823221138.45602-1-peterx@redhat.com> <411d7b8c-f914-875e-b397-856e6a894366@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=FPvAfMuF; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf09.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661529874; a=rsa-sha256; cv=none; b=FnpMEIaEru76wU63n13m/yOql5Dye+yiel2OJPmQXPMtsoNM+N3dQqJ3AnVDpqJNNopdIu /8PaOVDwIcyZ0ABNPRk0UGOQjF/7JZEjTOtHl0CSjIZjOlzsibIscAUebsPIMfGmwucpfy k/qlL5zxl19M9L+2UZdzEkvbMZBzYqA= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661529874; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=obYa+npn1GLmAkgYbBxpj4Xt3ZyWQyXIOu4icthPymg=; b=LC1t2dyTKzigtrgqa7XNMnfBTXkhqU+7QUH8IRn4hAi24v6nz6NyhvJ7k3q6ME8SAUE2Ks llGQFPCY9thYiLjB2j6VKAbFJOZ9HznGO+m8BlELwtXZIQ+jDtdwpX2oQZJk7UAOvOjVuA 8SfbSdE/y4AB0NFJkGJGmSiLZ5uQn3E= X-Rspam-User: X-Rspamd-Queue-Id: 2C32F140044 Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=FPvAfMuF; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf09.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com X-Stat-Signature: znof3fiautt7fksf9xo3gtaffuez4uu3 X-Rspamd-Server: rspam03 X-HE-Tag: 1661529873-286341 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Aug 26, 2022 at 04:39:08PM +0200, David Hildenbrand wrote: > On 26.08.22 16:25, Peter Xu wrote: > > On Fri, Aug 26, 2022 at 12:49:37PM +0200, David Hildenbrand wrote: > >> On 24.08.22 00:11, Peter Xu wrote: > >>> Yu Zhao reported a bug after the commit "mm/swap: Add swp_offset_pfn() to > >>> fetch PFN from swap entry" added a check in swp_offset_pfn() for swap type [1]: > >>> > >>> kernel BUG at include/linux/swapops.h:117! > >>> CPU: 46 PID: 5245 Comm: EventManager_De Tainted: G S O L 6.0.0-dbg-DEV #2 > >>> RIP: 0010:pfn_swap_entry_to_page+0x72/0xf0 > >>> Code: c6 48 8b 36 48 83 fe ff 74 53 48 01 d1 48 83 c1 08 48 8b 09 f6 > >>> c1 01 75 7b 66 90 48 89 c1 48 8b 09 f6 c1 01 74 74 5d c3 eb 9e <0f> 0b > >>> 48 ba ff ff ff ff 03 00 00 00 eb ae a9 ff 0f 00 00 75 13 48 > >>> RSP: 0018:ffffa59e73fabb80 EFLAGS: 00010282 > >>> RAX: 00000000ffffffe8 RBX: 0c00000000000000 RCX: ffffcd5440000000 > >>> RDX: 1ffffffffff7a80a RSI: 0000000000000000 RDI: 0c0000000000042b > >>> RBP: ffffa59e73fabb80 R08: ffff9965ca6e8bb8 R09: 0000000000000000 > >>> R10: ffffffffa5a2f62d R11: 0000030b372e9fff R12: ffff997b79db5738 > >>> R13: 000000000000042b R14: 0c0000000000042b R15: 1ffffffffff7a80a > >>> FS: 00007f549d1bb700(0000) GS:ffff99d3cf680000(0000) knlGS:0000000000000000 > >>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > >>> CR2: 0000440d035b3180 CR3: 0000002243176004 CR4: 00000000003706e0 > >>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > >>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > >>> Call Trace: > >>> > >>> change_pte_range+0x36e/0x880 > >>> change_p4d_range+0x2e8/0x670 > >>> change_protection_range+0x14e/0x2c0 > >>> mprotect_fixup+0x1ee/0x330 > >>> do_mprotect_pkey+0x34c/0x440 > >>> __x64_sys_mprotect+0x1d/0x30 > >>> > >>> It triggers because pfn_swap_entry_to_page() could be called upon e.g. a > >>> genuine swap entry. > >>> > >>> Fix it by only calling it when it's a write migration entry where the page* > >>> is used. > >>> > >>> [1] https://lore.kernel.org/lkml/CAOUHufaVC2Za-p8m0aiHw6YkheDcrO-C3wRGixwDS32VTS+k1w@mail.gmail.com/ > >>> > >>> Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive") > >>> Cc: David Hildenbrand > >>> Cc: > >>> Reported-by: Yu Zhao > >>> Signed-off-by: Peter Xu > >>> --- > >>> mm/mprotect.c | 3 ++- > >>> 1 file changed, 2 insertions(+), 1 deletion(-) > >>> > >>> diff --git a/mm/mprotect.c b/mm/mprotect.c > >>> index f2b9b1da9083..4549f5945ebe 100644 > >>> --- a/mm/mprotect.c > >>> +++ b/mm/mprotect.c > >>> @@ -203,10 +203,11 @@ static unsigned long change_pte_range(struct mmu_gather *tlb, > >>> pages++; > >>> } else if (is_swap_pte(oldpte)) { > >>> swp_entry_t entry = pte_to_swp_entry(oldpte); > >>> - struct page *page = pfn_swap_entry_to_page(entry); > >>> pte_t newpte; > >>> > >>> if (is_writable_migration_entry(entry)) { > >>> + struct page *page = pfn_swap_entry_to_page(entry); > >>> + > >>> /* > >>> * A protection check is difficult so > >>> * just be safe and disable write > >> > >> > >> Stumbling over the THP code, I was wondering if we also want to adjust change_huge_pmd() > >> and hugetlb_change_protection. There are no actual swap entries, so I assume we're fine. > >> > >> > >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c > >> index 482c1826e723..466364e7fc5f 100644 > >> --- a/mm/huge_memory.c > >> +++ b/mm/huge_memory.c > >> @@ -1798,10 +1798,10 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > >> #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION > >> if (is_swap_pmd(*pmd)) { > >> swp_entry_t entry = pmd_to_swp_entry(*pmd); > >> - struct page *page = pfn_swap_entry_to_page(entry); > >> > >> VM_BUG_ON(!is_pmd_migration_entry(*pmd)); > >> if (is_writable_migration_entry(entry)) { > >> + struct page *page = pfn_swap_entry_to_page(entry); > >> pmd_t newpmd; > >> /* > >> * A protection check is difficult so > >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c > >> index 2480ba627aa5..559465fae5cd 100644 > >> --- a/mm/hugetlb.c > >> +++ b/mm/hugetlb.c > >> @@ -6370,9 +6370,9 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, > >> } > >> if (unlikely(is_hugetlb_entry_migration(pte))) { > >> swp_entry_t entry = pte_to_swp_entry(pte); > >> - struct page *page = pfn_swap_entry_to_page(entry); > >> > >> if (!is_readable_migration_entry(entry)) { > >> + struct page *page = pfn_swap_entry_to_page(entry); > >> pte_t newpte; > >> > >> if (PageAnon(page)) > >> > >> > >> @Peter, what's your thought? > > > > IMHO they're not needed? > > > > The rule is simple in my mind: we should only pass in a pfn-typed swap > > entry into pfn_swap_entry_to_page() (or the new swp_offset_pfn()), or it's > > a violation of the API. In these two cases they do not violate the API and > > they're always safe because they're guaranteed to be pfn swap entries when > > calling. > > I was wondering about extreme corner cases regarding the struct page. > > Assume we have a hwpoison_entry that pointed at a valid struct page. We > can succeed in offlining+removing the section it's located on (I was > recently challenging if we want to keep that behavior as it's really > shaky already), freeing the relevant memmap entry and the memory section. > > pfn_swap_entry_to_page() -> pfn_to_page() would be problematic if there > is no memmap anymore. > > > I assume it's ok to always call it for is_pfn_swap_entry(), but in the > PMD case we only check for is_swap_pmd()? Isn't that problematic? I don't know extensively enough on hwpoison on validity of fetching page from pfn inside on online/offline ops, but.. if the only concern is about hwpoison entry existance here I think its fine? Because iirc we'l split thp when any of the subpage got poisoned, so we should never hit a hwpoison entry in thp path. > > > I was confused by the hugetlb case, it's indeed fine as we check for > is_hugetlb_entry_migration(). Right, it's more straightforward in the hugetlb case. -- Peter Xu