From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id A8C738E00E5 for ; Wed, 12 Dec 2018 12:27:23 -0500 (EST) Received: by mail-ed1-f72.google.com with SMTP id z10so8873035edz.15 for ; Wed, 12 Dec 2018 09:27:23 -0800 (PST) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com. [148.163.158.5]) by mx.google.com with ESMTPS id q10-v6si2701968ejf.1.2018.12.12.09.27.21 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 12 Dec 2018 09:27:21 -0800 (PST) Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wBCHJY79140390 for ; Wed, 12 Dec 2018 12:27:20 -0500 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0b-001b2d01.pphosted.com with ESMTP id 2pb5y2a73y-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 12 Dec 2018 12:27:20 -0500 Received: from localhost by e06smtp04.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 12 Dec 2018 17:27:18 -0000 From: Mikhail Zaslonko Subject: [PATCH v2 1/1] mm, memory_hotplug: Initialize struct pages for the full memory section Date: Wed, 12 Dec 2018 18:27:12 +0100 In-Reply-To: <20181212172712.34019-1-zaslonko@linux.ibm.com> References: <20181212172712.34019-1-zaslonko@linux.ibm.com> Message-Id: <20181212172712.34019-2-zaslonko@linux.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, Pavel.Tatashin@microsoft.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, gerald.schaefer@de.ibm.com, zaslonko@linux.ibm.com If memory end is not aligned with the sparse memory section boundary, the mapping of such a section is only partly initialized. This may lead to VM_BUG_ON due to uninitialized struct page access from is_mem_section_removable() or test_pages_in_a_zone() function triggered by memory_hotplug sysfs handlers: Here are the the panic examples: CONFIG_DEBUG_VM=y CONFIG_DEBUG_VM_PGFLAGS=y kernel parameter mem=2050M -------------------------- page:000003d082008000 is uninitialized and poisoned page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) Call Trace: ([<0000000000385b26>] test_pages_in_a_zone+0xde/0x160) [<00000000008f15c4>] show_valid_zones+0x5c/0x190 [<00000000008cf9c4>] dev_attr_show+0x34/0x70 [<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148 [<00000000003e4194>] seq_read+0x204/0x480 [<00000000003b53ea>] __vfs_read+0x32/0x178 [<00000000003b55b2>] vfs_read+0x82/0x138 [<00000000003b5be2>] ksys_read+0x5a/0xb0 [<0000000000b86ba0>] system_call+0xdc/0x2d8 Last Breaking-Event-Address: [<0000000000385b26>] test_pages_in_a_zone+0xde/0x160 Kernel panic - not syncing: Fatal exception: panic_on_oops kernel parameter mem=3075M -------------------------- page:000003d08300c000 is uninitialized and poisoned page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) Call Trace: ([<000000000038596c>] is_mem_section_removable+0xb4/0x190) [<00000000008f12fa>] show_mem_removable+0x9a/0xd8 [<00000000008cf9c4>] dev_attr_show+0x34/0x70 [<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148 [<00000000003e4194>] seq_read+0x204/0x480 [<00000000003b53ea>] __vfs_read+0x32/0x178 [<00000000003b55b2>] vfs_read+0x82/0x138 [<00000000003b5be2>] ksys_read+0x5a/0xb0 [<0000000000b86ba0>] system_call+0xdc/0x2d8 Last Breaking-Event-Address: [<000000000038596c>] is_mem_section_removable+0xb4/0x190 Kernel panic - not syncing: Fatal exception: panic_on_oops Fix the problem by initializing the last memory section of each zone in memmap_init_zone() till the very end, even if it goes beyond the zone end. Signed-off-by: Mikhail Zaslonko Reviewed-by: Gerald Schaefer Cc: --- mm/page_alloc.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2ec9cc407216..e2afdb2dc2c5 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5542,6 +5542,18 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, cond_resched(); } } +#ifdef CONFIG_SPARSEMEM + /* + * If the zone does not span the rest of the section then + * we should at least initialize those pages. Otherwise we + * could blow up on a poisoned page in some paths which depend + * on full sections being initialized (e.g. memory hotplug). + */ + while (end_pfn % PAGES_PER_SECTION) { + __init_single_page(pfn_to_page(end_pfn), end_pfn, zone, nid); + end_pfn++; + } +#endif } #ifdef CONFIG_ZONE_DEVICE -- 2.16.4