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 D3618ECAAA3 for ; Fri, 26 Aug 2022 16:35:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 34D8E940007; Fri, 26 Aug 2022 12:35:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2FCA46B0075; Fri, 26 Aug 2022 12:35:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 19E74940007; Fri, 26 Aug 2022 12:35:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 07DDD6B0074 for ; Fri, 26 Aug 2022 12:35:42 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id B9A6DC06A8 for ; Fri, 26 Aug 2022 16:35:41 +0000 (UTC) X-FDA: 79842294882.04.3FE5921 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 0F93314003F for ; Fri, 26 Aug 2022 16:35:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1661531740; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xJrtDOE1LS6YjgDSPmg59up2c2x/o9+GnjMuyWVSMCo=; b=d3UUSFIsd0uDWBQrlexVVQpHjSWUIuPoIVbzdujCj0dnUEyknNOa3tuwWoBdjOlWABagRD of+shh5qJtPHL3m2qfcxS36l6jOcJvHc83QcR3b+D9LbIFbd7AiDNwqMKuE+Bu27V4EYLa sjeoTTDmw9Il9F29HZGZ7ESvFCimTtE= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-612-fxP9PVFbNC218UOCEMwJgg-1; Fri, 26 Aug 2022 12:35:39 -0400 X-MC-Unique: fxP9PVFbNC218UOCEMwJgg-1 Received: by mail-wm1-f71.google.com with SMTP id f7-20020a1c6a07000000b003a60ede816cso690667wmc.0 for ; Fri, 26 Aug 2022 09:35:39 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:organization:from:references :cc:to:content-language:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc; bh=xJrtDOE1LS6YjgDSPmg59up2c2x/o9+GnjMuyWVSMCo=; b=GC0HIkLOH67omEKqYtrP3jHbRCD8ybr9Yf4/vELOl73LIrsDGoAmVJWSpOvPUMWgdI jwE7LTq+46eMGHe+oKpLHN74r7D0ZcIrcN/W3hwnvIgT5LCPB6k/A60sf0U2hr7K3RJx nnx8LkyjYi90H+nbvqG5dB55+QwoM5XoZ7AYJLx9vysZquxTOa2SBsfZGQljTerT3TVC pKIzRG4XefZarvcDxH2tNeCTbwh99UTF+zboO/zeP87CYr8KwbxcQXtJd072xzzhzw6Q o8Xl5erWt4EGmKi5lOMNolfharIxHYqvSMKFaxxYG/W76TuBMDhYIbAa9rC/zfIX8l+H 5jgw== X-Gm-Message-State: ACgBeo0n7GDpRZ57b1gvMsa/b9yAXQAOeVgyDIxEmgwpoGewiGHxxfri gEd+ixGyeFFn02CHH7vJu2/si4uVyzLSSyY2k7K65M3RU+ezRnTvqLZpGczqpN1b1xC6SZvZ5HX WRcCc4w/L0eE= X-Received: by 2002:a05:600c:290a:b0:3a5:515d:4f69 with SMTP id i10-20020a05600c290a00b003a5515d4f69mr244849wmd.127.1661531738256; Fri, 26 Aug 2022 09:35:38 -0700 (PDT) X-Google-Smtp-Source: AA6agR5EIHMKQi/zXPpLKIV0JdmfWhkQBXmKVB2m1LedfaFyGwzgbKghd2AEaeUXKNQ8MGWtQi3a4A== X-Received: by 2002:a05:600c:290a:b0:3a5:515d:4f69 with SMTP id i10-20020a05600c290a00b003a5515d4f69mr244839wmd.127.1661531737961; Fri, 26 Aug 2022 09:35:37 -0700 (PDT) Received: from ?IPV6:2003:cb:c708:f600:abad:360:c840:33fa? (p200300cbc708f600abad0360c84033fa.dip0.t-ipconnect.de. [2003:cb:c708:f600:abad:360:c840:33fa]) by smtp.gmail.com with ESMTPSA id m21-20020a05600c4f5500b003a327b98c0asm102915wmq.22.2022.08.26.09.35.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 26 Aug 2022 09:35:37 -0700 (PDT) Message-ID: Date: Fri, 26 Aug 2022 18:35:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH] mm/mprotect: Only reference swap pfn page if type match To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Huang Ying , stable@vger.kernel.org, Yu Zhao References: <20220823221138.45602-1-peterx@redhat.com> <411d7b8c-f914-875e-b397-856e6a894366@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661531741; a=rsa-sha256; cv=none; b=7bFH+uZNIv4I7dhfo7zFs1qqczlx1ArNn5tC1lsH3f5qea+TQhcM4G1eqqwtDtlGKzwkF9 Uj0Q8xje4sBf9Ek4Nzh8+hqejPmixR1uAtQk4xoeDOujOg4UPeLJrYFwrtX/dZKLr5tWwK tsQzCv9hJi03qThiQPJdXSmKfTpM/ns= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=d3UUSFIs; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf09.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661531741; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=xJrtDOE1LS6YjgDSPmg59up2c2x/o9+GnjMuyWVSMCo=; b=UjjZpVBfD0eHSGNKpgITj5030gqBIGfXpS3FaLmcXlKkM0Eiadq43Lco1k3OQrGDnATbJX ZM7kLTw3MF2EbH5A1/cP36srmGoaXJsEnOFYNr0mjIpMWYGQkDKa9iz6h4H2ojJWpzisrf aw+gzJHe/NlEIJqMulFs/pIU7Js1O2E= Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=d3UUSFIs; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf09.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: kbhk69jtna7zc38kwm4yxwyd5as7hywa X-Rspamd-Queue-Id: 0F93314003F X-HE-Tag: 1661531740-121957 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 26.08.22 18:04, Peter Xu wrote: > 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. Ah right, so we're good. Thanks! -- Thanks, David / dhildenb