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=-8.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable 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 85017C4360F for ; Wed, 20 Feb 2019 12:57:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4BF162147A for ; Wed, 20 Feb 2019 12:57:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550667461; bh=B3DnydBaefWZ5Mz865juh4aTutgFiH3xnzyN41m3mNo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=VUHGL/z56OnD79AqqczSRHlrpX/4karCaMnPuVLeo2815j61ruXBOZq/KRJkHCgtI DALjv6ZuRtKSMPCuEIPoM2jYnvR9l7u4ICopsmHDq+OO2QTqsZI8eQFdoUhrmD2dgJ i4fM2t5C8jBmmMFipsV7T4R5nlkVIRo9Q2WsfOgE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728083AbfBTM5j (ORCPT ); Wed, 20 Feb 2019 07:57:39 -0500 Received: from mx2.suse.de ([195.135.220.15]:53372 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726172AbfBTM5j (ORCPT ); Wed, 20 Feb 2019 07:57:39 -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 D3C32AF82; Wed, 20 Feb 2019 12:57:36 +0000 (UTC) Date: Wed, 20 Feb 2019 13:57:32 +0100 From: Michal Hocko To: kernel test robot Cc: Andrew Morton , Mike Rapoport , Matthew Wilcox , Oscar Salvador , linux-mm@kvack.org, LKML , lkp@01.org Subject: Re: [RFC PATCH] mm, memory_hotplug: fix off-by-one in is_pageblock_removable Message-ID: <20190220125732.GB4525@dhcp22.suse.cz> References: <20190218052823.GH29177@shao2-debian> <20190218181544.14616-1-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190218181544.14616-1-mhocko@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Rong Chen, coudl you double check this indeed fixes the issue for you please? On Mon 18-02-19 19:15:44, Michal Hocko wrote: > From: Michal Hocko > > Rong Chen has reported the following boot crash > [ 40.305212] PGD 0 P4D 0 > [ 40.308255] Oops: 0000 [#1] PREEMPT SMP PTI > [ 40.313055] CPU: 1 PID: 239 Comm: udevd Not tainted 5.0.0-rc4-00149-gefad4e4 #1 > [ 40.321348] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 > [ 40.330813] RIP: 0010:page_mapping+0x12/0x80 > [ 40.335709] Code: 5d c3 48 89 df e8 0e ad 02 00 85 c0 75 da 89 e8 5b 5d c3 0f 1f 44 00 00 53 48 89 fb 48 8b 43 08 48 8d 50 ff a8 01 48 0f 45 da <48> 8b 53 08 48 8d 42 ff 83 e2 01 48 0f 44 c3 48 83 38 ff 74 2f 48 > [ 40.356704] RSP: 0018:ffff88801fa87cd8 EFLAGS: 00010202 > [ 40.362714] RAX: ffffffffffffffff RBX: fffffffffffffffe RCX: 000000000000000a > [ 40.370798] RDX: fffffffffffffffe RSI: ffffffff820b9a20 RDI: ffff88801e5c0000 > [ 40.378830] RBP: 6db6db6db6db6db7 R08: ffff88801e8bb000 R09: 0000000001b64d13 > [ 40.386902] R10: ffff88801fa87cf8 R11: 0000000000000001 R12: ffff88801e640000 > [ 40.395033] R13: ffffffff820b9a20 R14: ffff88801f145258 R15: 0000000000000001 > [ 40.403138] FS: 00007fb2079817c0(0000) GS:ffff88801dd00000(0000) knlGS:0000000000000000 > [ 40.412243] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 40.418846] CR2: 0000000000000006 CR3: 000000001fa82000 CR4: 00000000000006a0 > [ 40.426951] Call Trace: > [ 40.429843] __dump_page+0x14/0x2c0 > [ 40.433947] is_mem_section_removable+0x24c/0x2c0 > [ 40.439327] removable_show+0x87/0xa0 > [ 40.443613] dev_attr_show+0x25/0x60 > [ 40.447763] sysfs_kf_seq_show+0xba/0x110 > [ 40.452363] seq_read+0x196/0x3f0 > [ 40.456282] __vfs_read+0x34/0x180 > [ 40.460233] ? lock_acquire+0xb6/0x1e0 > [ 40.464610] vfs_read+0xa0/0x150 > [ 40.468372] ksys_read+0x44/0xb0 > [ 40.472129] ? do_syscall_64+0x1f/0x4a0 > [ 40.476593] do_syscall_64+0x5e/0x4a0 > [ 40.480809] ? trace_hardirqs_off_thunk+0x1a/0x1c > [ 40.486195] entry_SYSCALL_64_after_hwframe+0x49/0xbe > > and bisected it down to efad4e475c31 ("mm, memory_hotplug: > is_mem_section_removable do not pass the end of a zone"). The reason for > the crash is that the mapping is garbage for poisoned (uninitialized) page. > This shouldn't happen as all pages in the zone's boundary should be > initialized. Later debugging revealed that the actual problem is an > off-by-one when evaluating the end_page. start_pfn + nr_pages resp. > zone_end_pfn refers to a pfn after the range and as such it might belong > to a differen memory section. This along with CONFIG_SPARSEMEM then > makes the loop condition completely bogus because a pointer arithmetic > doesn't work for pages from two different sections in that memory model. > > Fix the issue by reworking is_pageblock_removable to be pfn based and > only use struct page where necessary. This makes the code slightly > easier to follow and we will remove the problematic pointer arithmetic > completely. > > Fixes: efad4e475c31 ("mm, memory_hotplug: is_mem_section_removable do not pass the end of a zone") > Reported-by: > Signed-off-by: Michal Hocko > --- > mm/memory_hotplug.c | 27 +++++++++++++++------------ > 1 file changed, 15 insertions(+), 12 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 124e794867c5..1ad28323fb9f 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1188,11 +1188,13 @@ static inline int pageblock_free(struct page *page) > return PageBuddy(page) && page_order(page) >= pageblock_order; > } > > -/* Return the start of the next active pageblock after a given page */ > -static struct page *next_active_pageblock(struct page *page) > +/* Return the pfn of the start of the next active pageblock after a given pfn */ > +static unsigned long next_active_pageblock(unsigned long pfn) > { > + struct page *page = pfn_to_page(pfn); > + > /* Ensure the starting page is pageblock-aligned */ > - BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1)); > + BUG_ON(pfn & (pageblock_nr_pages - 1)); > > /* If the entire pageblock is free, move to the end of free page */ > if (pageblock_free(page)) { > @@ -1200,16 +1202,16 @@ static struct page *next_active_pageblock(struct page *page) > /* be careful. we don't have locks, page_order can be changed.*/ > order = page_order(page); > if ((order < MAX_ORDER) && (order >= pageblock_order)) > - return page + (1 << order); > + return pfn + (1 << order); > } > > - return page + pageblock_nr_pages; > + return pfn + pageblock_nr_pages; > } > > -static bool is_pageblock_removable_nolock(struct page *page) > +static bool is_pageblock_removable_nolock(unsigned long pfn) > { > + struct page *page = pfn_to_page(pfn); > struct zone *zone; > - unsigned long pfn; > > /* > * We have to be careful here because we are iterating over memory > @@ -1232,13 +1234,14 @@ static bool is_pageblock_removable_nolock(struct page *page) > /* Checks if this range of memory is likely to be hot-removable. */ > bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages) > { > - struct page *page = pfn_to_page(start_pfn); > - unsigned long end_pfn = min(start_pfn + nr_pages, zone_end_pfn(page_zone(page))); > - struct page *end_page = pfn_to_page(end_pfn); > + unsigned long end_pfn, pfn; > + > + end_pfn = min(start_pfn + nr_pages, > + zone_end_pfn(page_zone(pfn_to_page(start_pfn)))); > > /* Check the starting page of each pageblock within the range */ > - for (; page < end_page; page = next_active_pageblock(page)) { > - if (!is_pageblock_removable_nolock(page)) > + for (pfn = start_pfn; pfn < end_pfn; pfn = next_active_pageblock(pfn)) { > + if (!is_pageblock_removable_nolock(pfn)) > return false; > cond_resched(); > } > -- > 2.20.1 > -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============7540554572065543124==" MIME-Version: 1.0 From: Michal Hocko To: lkp@lists.01.org Subject: Re: [RFC PATCH] mm, memory_hotplug: fix off-by-one in is_pageblock_removable Date: Wed, 20 Feb 2019 13:57:32 +0100 Message-ID: <20190220125732.GB4525@dhcp22.suse.cz> In-Reply-To: <20190218181544.14616-1-mhocko@kernel.org> List-Id: --===============7540554572065543124== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Rong Chen, coudl you double check this indeed fixes the issue for you please? On Mon 18-02-19 19:15:44, Michal Hocko wrote: > From: Michal Hocko > = > Rong Chen has reported the following boot crash > [ 40.305212] PGD 0 P4D 0 > [ 40.308255] Oops: 0000 [#1] PREEMPT SMP PTI > [ 40.313055] CPU: 1 PID: 239 Comm: udevd Not tainted 5.0.0-rc4-00149-ge= fad4e4 #1 > [ 40.321348] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIO= S 1.10.2-1 04/01/2014 > [ 40.330813] RIP: 0010:page_mapping+0x12/0x80 > [ 40.335709] Code: 5d c3 48 89 df e8 0e ad 02 00 85 c0 75 da 89 e8 5b 5= d c3 0f 1f 44 00 00 53 48 89 fb 48 8b 43 08 48 8d 50 ff a8 01 48 0f 45 da <= 48> 8b 53 08 48 8d 42 ff 83 e2 01 48 0f 44 c3 48 83 38 ff 74 2f 48 > [ 40.356704] RSP: 0018:ffff88801fa87cd8 EFLAGS: 00010202 > [ 40.362714] RAX: ffffffffffffffff RBX: fffffffffffffffe RCX: 000000000= 000000a > [ 40.370798] RDX: fffffffffffffffe RSI: ffffffff820b9a20 RDI: ffff88801= e5c0000 > [ 40.378830] RBP: 6db6db6db6db6db7 R08: ffff88801e8bb000 R09: 000000000= 1b64d13 > [ 40.386902] R10: ffff88801fa87cf8 R11: 0000000000000001 R12: ffff88801= e640000 > [ 40.395033] R13: ffffffff820b9a20 R14: ffff88801f145258 R15: 000000000= 0000001 > [ 40.403138] FS: 00007fb2079817c0(0000) GS:ffff88801dd00000(0000) knlG= S:0000000000000000 > [ 40.412243] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 40.418846] CR2: 0000000000000006 CR3: 000000001fa82000 CR4: 000000000= 00006a0 > [ 40.426951] Call Trace: > [ 40.429843] __dump_page+0x14/0x2c0 > [ 40.433947] is_mem_section_removable+0x24c/0x2c0 > [ 40.439327] removable_show+0x87/0xa0 > [ 40.443613] dev_attr_show+0x25/0x60 > [ 40.447763] sysfs_kf_seq_show+0xba/0x110 > [ 40.452363] seq_read+0x196/0x3f0 > [ 40.456282] __vfs_read+0x34/0x180 > [ 40.460233] ? lock_acquire+0xb6/0x1e0 > [ 40.464610] vfs_read+0xa0/0x150 > [ 40.468372] ksys_read+0x44/0xb0 > [ 40.472129] ? do_syscall_64+0x1f/0x4a0 > [ 40.476593] do_syscall_64+0x5e/0x4a0 > [ 40.480809] ? trace_hardirqs_off_thunk+0x1a/0x1c > [ 40.486195] entry_SYSCALL_64_after_hwframe+0x49/0xbe > = > and bisected it down to efad4e475c31 ("mm, memory_hotplug: > is_mem_section_removable do not pass the end of a zone"). The reason for > the crash is that the mapping is garbage for poisoned (uninitialized) pag= e. > This shouldn't happen as all pages in the zone's boundary should be > initialized. Later debugging revealed that the actual problem is an > off-by-one when evaluating the end_page. start_pfn + nr_pages resp. > zone_end_pfn refers to a pfn after the range and as such it might belong > to a differen memory section. This along with CONFIG_SPARSEMEM then > makes the loop condition completely bogus because a pointer arithmetic > doesn't work for pages from two different sections in that memory model. > = > Fix the issue by reworking is_pageblock_removable to be pfn based and > only use struct page where necessary. This makes the code slightly > easier to follow and we will remove the problematic pointer arithmetic > completely. > = > Fixes: efad4e475c31 ("mm, memory_hotplug: is_mem_section_removable do not= pass the end of a zone") > Reported-by: > Signed-off-by: Michal Hocko > --- > mm/memory_hotplug.c | 27 +++++++++++++++------------ > 1 file changed, 15 insertions(+), 12 deletions(-) > = > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 124e794867c5..1ad28323fb9f 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1188,11 +1188,13 @@ static inline int pageblock_free(struct page *pag= e) > return PageBuddy(page) && page_order(page) >=3D pageblock_order; > } > = > -/* Return the start of the next active pageblock after a given page */ > -static struct page *next_active_pageblock(struct page *page) > +/* Return the pfn of the start of the next active pageblock after a give= n pfn */ > +static unsigned long next_active_pageblock(unsigned long pfn) > { > + struct page *page =3D pfn_to_page(pfn); > + > /* Ensure the starting page is pageblock-aligned */ > - BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1)); > + BUG_ON(pfn & (pageblock_nr_pages - 1)); > = > /* If the entire pageblock is free, move to the end of free page */ > if (pageblock_free(page)) { > @@ -1200,16 +1202,16 @@ static struct page *next_active_pageblock(struct = page *page) > /* be careful. we don't have locks, page_order can be changed.*/ > order =3D page_order(page); > if ((order < MAX_ORDER) && (order >=3D pageblock_order)) > - return page + (1 << order); > + return pfn + (1 << order); > } > = > - return page + pageblock_nr_pages; > + return pfn + pageblock_nr_pages; > } > = > -static bool is_pageblock_removable_nolock(struct page *page) > +static bool is_pageblock_removable_nolock(unsigned long pfn) > { > + struct page *page =3D pfn_to_page(pfn); > struct zone *zone; > - unsigned long pfn; > = > /* > * We have to be careful here because we are iterating over memory > @@ -1232,13 +1234,14 @@ static bool is_pageblock_removable_nolock(struct = page *page) > /* Checks if this range of memory is likely to be hot-removable. */ > bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_= pages) > { > - struct page *page =3D pfn_to_page(start_pfn); > - unsigned long end_pfn =3D min(start_pfn + nr_pages, zone_end_pfn(page_z= one(page))); > - struct page *end_page =3D pfn_to_page(end_pfn); > + unsigned long end_pfn, pfn; > + > + end_pfn =3D min(start_pfn + nr_pages, > + zone_end_pfn(page_zone(pfn_to_page(start_pfn)))); > = > /* Check the starting page of each pageblock within the range */ > - for (; page < end_page; page =3D next_active_pageblock(page)) { > - if (!is_pageblock_removable_nolock(page)) > + for (pfn =3D start_pfn; pfn < end_pfn; pfn =3D next_active_pageblock(pf= n)) { > + if (!is_pageblock_removable_nolock(pfn)) > return false; > cond_resched(); > } > -- = > 2.20.1 > = -- = Michal Hocko SUSE Labs --===============7540554572065543124==--