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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 968A2C43603 for ; Wed, 4 Dec 2019 18:27:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 696D1205F4 for ; Wed, 4 Dec 2019 18:27:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729361AbfLDS1w (ORCPT ); Wed, 4 Dec 2019 13:27:52 -0500 Received: from mx2.suse.de ([195.135.220.15]:60136 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728328AbfLDS1u (ORCPT ); Wed, 4 Dec 2019 13:27:50 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 9D3CDB256; Wed, 4 Dec 2019 18:27:46 +0000 (UTC) Subject: Re: [PATCH 4.9 105/125] mm, gup: add missing refcount overflow checks on x86 and s390 To: Greg Kroah-Hartman , linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, Sasha Levin , Ben Hutchings References: <20191204175308.377746305@linuxfoundation.org> <20191204175325.500930880@linuxfoundation.org> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; prefer-encrypt=mutual; keydata= mQINBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD 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hBM8hvtsyq8lq8vJOxv6XD6xcTtj5Az8t2JjdUX6SF9hxJpwhBU0wrCoGDkWp4Bbv6jnF7zP Nzftr4l8RuJoywDIiJpdaNpSlXKpj/K6KrnyAI/joYc7 Message-ID: <7ca516fa-c526-b5e6-4b7c-855f229112ac@suse.cz> Date: Wed, 4 Dec 2019 19:27:44 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.1 MIME-Version: 1.0 In-Reply-To: <20191204175325.500930880@linuxfoundation.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/4/19 6:56 PM, Greg Kroah-Hartman wrote: > From: Vlastimil Babka > > The mainline commit 8fde12ca79af ("mm: prevent get_user_pages() from > overflowing page refcount") was backported to 4.9.y stable as commit > 2ed768cfd895. The backport however missed that in 4.9, there are several > arch-specific gup.c versions with fast gup implementations, so these do not > prevent refcount overflow. > > This is partially fixed for x86 in stable-only commit d73af79742e7 ("x86, mm, > gup: prevent get_page() race with munmap in paravirt guest"). This stable-only > commit adds missing parts to x86 version, as well as s390 version, both taken > from the SUSE SLES/openSUSE 4.12-based kernels. > > The remaining architectures with own gup.c are sparc, mips, sh. It's unlikely > the known overflow scenario based on FUSE, which needs 140GB of RAM, is a > problem for those architectures, and I don't feel confident enough to patch > them. > > Signed-off-by: Vlastimil Babka > Signed-off-by: Sasha Levin No, this one had a leak bug and I've sent updated version: https://lore.kernel.org/linux-mm/e274291b-054f-2fad-28e8-59fabf312e61@suse.cz/ > --- > arch/s390/mm/gup.c | 9 ++++++--- > arch/x86/mm/gup.c | 10 ++++++++-- > 2 files changed, 14 insertions(+), 5 deletions(-) > > diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c > index 97fc449a74707..33a940389a6d1 100644 > --- a/arch/s390/mm/gup.c > +++ b/arch/s390/mm/gup.c > @@ -38,7 +38,8 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr, > VM_BUG_ON(!pfn_valid(pte_pfn(pte))); > page = pte_page(pte); > head = compound_head(page); > - if (!page_cache_get_speculative(head)) > + if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0) > + || !page_cache_get_speculative(head))) > return 0; > if (unlikely(pte_val(pte) != pte_val(*ptep))) { > put_page(head); > @@ -76,7 +77,8 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr, > refs++; > } while (addr += PAGE_SIZE, addr != end); > > - if (!page_cache_add_speculative(head, refs)) { > + if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0) > + || !page_cache_add_speculative(head, refs))) { > *nr -= refs; > return 0; > } > @@ -150,7 +152,8 @@ static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr, > refs++; > } while (addr += PAGE_SIZE, addr != end); > > - if (!page_cache_add_speculative(head, refs)) { > + if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0) > + || !page_cache_add_speculative(head, refs))) { > *nr -= refs; > return 0; > } > diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c > index d7db45bdfb3bd..551fc7fea046d 100644 > --- a/arch/x86/mm/gup.c > +++ b/arch/x86/mm/gup.c > @@ -202,10 +202,12 @@ static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr, > undo_dev_pagemap(nr, nr_start, pages); > return 0; > } > + if (unlikely(!try_get_page(page))) { > + put_dev_pagemap(pgmap); > + return 0; > + } > SetPageReferenced(page); > pages[*nr] = page; > - get_page(page); > - put_dev_pagemap(pgmap); > (*nr)++; > pfn++; > } while (addr += PAGE_SIZE, addr != end); > @@ -230,6 +232,8 @@ static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr, > > refs = 0; > head = pmd_page(pmd); > + if (WARN_ON_ONCE(page_ref_count(head) <= 0)) > + return 0; > page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); > do { > VM_BUG_ON_PAGE(compound_head(page) != head, page); > @@ -289,6 +293,8 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr, > > refs = 0; > head = pud_page(pud); > + if (WARN_ON_ONCE(page_ref_count(head) <= 0)) > + return 0; > page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); > do { > VM_BUG_ON_PAGE(compound_head(page) != head, page); >