From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-3863680-1516366682-2-8107099311268334725 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', FromHeader='org', MailFrom='org' X-Spam-charsets: plain='us-ascii' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1516366682; b=aKQGo9cJFJ3ZM48skEbd3Tn6dGVN4NsEvlt8i5ulrgoafTU oVconiFqw7gTJbK/mqHpYd6D7eKIN5L37xOy9XpXpMIpsDjjwG1u4tmB5u7SgVDp nqzk7IAl8XPQnwqkfjwqqzVSQn0TiPLypQYxiwCdrYf/lfnE2ZA2nms63ROH6U42 6Ytc+kHLZs5INA1Atbvtp+SrQsvt9N6vjlRk/NNgj39nkLeHIz6Cifssjx3ppUt5 tdkLDt2889uaDNYvBxKzHfCo55de5LBWG47lLouD1cJN7gYFgH2oTM54a3+gwdKh ohljvW8kIS1r0ETPorO01bv6VQL/v6vFYye0yCQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to:sender :list-id; s=arctest; t=1516366682; bh=ieqN5aDExYiaShUHZ13AA39k+2 ui5UXnnfaVfuoj0p0=; b=YAGvPWu4pQ9Bqt7E1IkCH6jD9smt4k764dmerzOgMC R333OKgbEYN9K+kmWWMEYI5eXl3jboHobFgZUzl1ulHgk4NU/HFBrofXywQnZcjt pozB7GbA1IsKPJKjU/F3DVTLH6WRXsd2wogfQqyyMFoGVYp3fQtWqkR7ro4r+CSK Gbu1ZxYWQNp6Q/G1CK4HkmjpODCSdjfyUaN6ahjSkpv5ganNLoyNXRH3dhQmlM1F J1UR/9IDRE23sN0VBKshINDCn2rynOIA5de6fXQE8TXxXe4hQcq1qiiH1jFrrCZU kuTyIaJB/VjS0dPtZbVX7m1Ap1vyCKwhKID5VMO9vikQ== ARC-Authentication-Results: i=1; mx6.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=kernel.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=orgdomain_pass; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=kernel.org header.result=pass header_is_org_domain=yes Authentication-Results: mx6.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=kernel.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=orgdomain_pass; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=kernel.org header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754759AbeASM5p (ORCPT ); Fri, 19 Jan 2018 07:57:45 -0500 Received: from mx2.suse.de ([195.135.220.15]:58788 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755175AbeASM5K (ORCPT ); Fri, 19 Jan 2018 07:57:10 -0500 Date: Fri, 19 Jan 2018 13:57:07 +0100 From: Michal Hocko To: "Kirill A. Shutemov" Cc: akpm@linux-foundation.org, penguin-kernel@I-love.SAKURA.ne.jp, torvalds@linux-foundation.org, aarcange@redhat.com, dave.hansen@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCHv2] mm, page_vma_mapped: Drop faulty pointer arithmetics in check_pte() Message-ID: <20180119125707.GB6584@dhcp22.suse.cz> References: <20180119124924.25642-1-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180119124924.25642-1-kirill.shutemov@linux.intel.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Fri 19-01-18 15:49:24, Kirill A. Shutemov wrote: > Tetsuo reported random crashes under memory pressure on 32-bit x86 > system and tracked down to change that introduced > page_vma_mapped_walk(). > > The root cause of the issue is the faulty pointer math in check_pte(). > As ->pte may point to an arbitrary page we have to check that they are > belong to the section before doing math. Otherwise it may lead to weird > results. > > It wasn't noticed until now as mem_map[] is virtually contiguous on > flatmem or vmemmap sparsemem. Pointer arithmetic just works against all > 'struct page' pointers. But with classic sparsemem, it doesn't because > each section memap is allocated separately and so consecutive pfns > crossing two sections might have struct pages at completely unrelated > addresses. > > Let's restructure code a bit and replace pointer arithmetic with > operations on pfns. > > Signed-off-by: Kirill A. Shutemov > Reported-by: Tetsuo Handa > Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()") > Cc: stable@vger.kernel.org Much better. Thanks! Acked-by: Michal Hocko > --- > v2: > - Do not use uninitialized 'pfn' for !MIGRATION case (Michal) > > --- > include/linux/swapops.h | 21 +++++++++++++++++ > mm/page_vma_mapped.c | 63 +++++++++++++++++++++++++++++-------------------- > 2 files changed, 59 insertions(+), 25 deletions(-) > > diff --git a/include/linux/swapops.h b/include/linux/swapops.h > index 9c5a2628d6ce..1d3877c39a00 100644 > --- a/include/linux/swapops.h > +++ b/include/linux/swapops.h > @@ -124,6 +124,11 @@ static inline bool is_write_device_private_entry(swp_entry_t entry) > return unlikely(swp_type(entry) == SWP_DEVICE_WRITE); > } > > +static inline unsigned long device_private_entry_to_pfn(swp_entry_t entry) > +{ > + return swp_offset(entry); > +} > + > static inline struct page *device_private_entry_to_page(swp_entry_t entry) > { > return pfn_to_page(swp_offset(entry)); > @@ -154,6 +159,11 @@ static inline bool is_write_device_private_entry(swp_entry_t entry) > return false; > } > > +static inline unsigned long device_private_entry_to_pfn(swp_entry_t entry) > +{ > + return 0; > +} > + > static inline struct page *device_private_entry_to_page(swp_entry_t entry) > { > return NULL; > @@ -189,6 +199,11 @@ static inline int is_write_migration_entry(swp_entry_t entry) > return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE); > } > > +static inline unsigned long migration_entry_to_pfn(swp_entry_t entry) > +{ > + return swp_offset(entry); > +} > + > static inline struct page *migration_entry_to_page(swp_entry_t entry) > { > struct page *p = pfn_to_page(swp_offset(entry)); > @@ -218,6 +233,12 @@ static inline int is_migration_entry(swp_entry_t swp) > { > return 0; > } > + > +static inline unsigned long migration_entry_to_pfn(swp_entry_t entry) > +{ > + return 0; > +} > + > static inline struct page *migration_entry_to_page(swp_entry_t entry) > { > return NULL; > diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c > index d22b84310f6d..956015614395 100644 > --- a/mm/page_vma_mapped.c > +++ b/mm/page_vma_mapped.c > @@ -30,10 +30,29 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw) > return true; > } > > +/** > + * check_pte - check if @pvmw->page is mapped at the @pvmw->pte > + * > + * page_vma_mapped_walk() found a place where @pvmw->page is *potentially* > + * mapped. check_pte() has to validate this. > + * > + * @pvmw->pte may point to empty PTE, swap PTE or PTE pointing to arbitrary > + * page. > + * > + * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration > + * entry that points to @pvmw->page or any subpage in case of THP. > + * > + * If PVMW_MIGRATION flag is not set, returns true if @pvmw->pte points to > + * @pvmw->page or any subpage in case of THP. > + * > + * Otherwise, return false. > + * > + */ > static bool check_pte(struct page_vma_mapped_walk *pvmw) > { > + unsigned long pfn; > + > if (pvmw->flags & PVMW_MIGRATION) { > -#ifdef CONFIG_MIGRATION > swp_entry_t entry; > if (!is_swap_pte(*pvmw->pte)) > return false; > @@ -41,37 +60,31 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw) > > if (!is_migration_entry(entry)) > return false; > - if (migration_entry_to_page(entry) - pvmw->page >= > - hpage_nr_pages(pvmw->page)) { > - return false; > - } > - if (migration_entry_to_page(entry) < pvmw->page) > - return false; > -#else > - WARN_ON_ONCE(1); > -#endif > - } else { > - if (is_swap_pte(*pvmw->pte)) { > - swp_entry_t entry; > > - entry = pte_to_swp_entry(*pvmw->pte); > - if (is_device_private_entry(entry) && > - device_private_entry_to_page(entry) == pvmw->page) > - return true; > - } > + pfn = migration_entry_to_pfn(entry); > + } else if (is_swap_pte(*pvmw->pte)) { > + swp_entry_t entry; > > - if (!pte_present(*pvmw->pte)) > + /* Handle un-addressable ZONE_DEVICE memory */ > + entry = pte_to_swp_entry(*pvmw->pte); > + if (!is_device_private_entry(entry)) > return false; > > - /* THP can be referenced by any subpage */ > - if (pte_page(*pvmw->pte) - pvmw->page >= > - hpage_nr_pages(pvmw->page)) { > - return false; > - } > - if (pte_page(*pvmw->pte) < pvmw->page) > + pfn = device_private_entry_to_pfn(entry); > + } else { > + if (!pte_present(*pvmw->pte)) > return false; > + > + pfn = pte_pfn(*pvmw->pte); > } > > + if (pfn < page_to_pfn(pvmw->page)) > + return false; > + > + /* THP can be referenced by any subpage */ > + if (pfn - page_to_pfn(pvmw->page) >= hpage_nr_pages(pvmw->page)) > + return false; > + > return true; > } > > -- > 2.15.1 -- Michal Hocko SUSE Labs