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[37.188.142.190]) by smtp.gmail.com with ESMTPSA id l19sm1491875wme.21.2019.01.30.01.12.28 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 30 Jan 2019 01:12:29 -0800 (PST) From: Michal Hocko To: Mikhail Zaslonko , Mikhail Gavrilov Cc: Andrew Morton , Pavel Tatashin , schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, gerald.schaefer@de.ibm.com, , LKML , Oscar Salvador , Michal Hocko Subject: [PATCH v2 2/2] mm, memory_hotplug: test_pages_in_a_zone do not pass the end of zone Date: Wed, 30 Jan 2019 10:12:17 +0100 Message-Id: <20190130091217.24467-3-mhocko@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190130091217.24467-1-mhocko@kernel.org> References: <20190130091217.24467-1-mhocko@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mikhail Zaslonko 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 pages access from test_pages_in_a_zone() function triggered by memory_hotplug sysfs handlers. Here are the the panic examples: 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 Fix this by checking whether the pfn to check is within the zone. [mhocko@suse.com: separated this change from http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com] Reviewed-by: Oscar Salvador Tested-by: Gerald Schaefer Tested-by: Mikhail Gavrilov Signed-off-by: Mikhail Zaslonko Signed-off-by: Michal Hocko --- mm/memory_hotplug.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 07872789d778..7711d0e327b6 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1274,6 +1274,9 @@ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn, i++; if (i == MAX_ORDER_NR_PAGES || pfn + i >= end_pfn) continue; + /* Check if we got outside of the zone */ + if (zone && !zone_spans_pfn(zone, pfn + i)) + return 0; page = pfn_to_page(pfn + i); if (zone && page_zone(page) != zone) return 0; -- 2.20.1