mm, memory_hotplug: initialize struct pages for the full memory section

mzaslonk · torvalds · commit 2830bf6f05fb · 2018-12-21T14:51:18.000-08:00
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: ( test_pages_in_a_zone+0xde/0x160) show_valid_zones+0x5c/0x190 dev_attr_show+0x34/0x70 sysfs_kf_seq_show+0xc8/0x148 seq_read+0x204/0x480 __vfs_read+0x32/0x178 vfs_read+0x82/0x138 ksys_read+0x5a/0xb0 system_call+0xdc/0x2d8 Last Breaking-Event-Address: 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: ( is_mem_section_removable+0xb4/0x190) show_mem_removable+0x9a/0xd8 dev_attr_show+0x34/0x70 sysfs_kf_seq_show+0xc8/0x148 seq_read+0x204/0x480 __vfs_read+0x32/0x178 vfs_read+0x82/0x138 ksys_read+0x5a/0xb0 system_call+0xdc/0x2d8 Last Breaking-Event-Address: 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. Michal said: : This has alwways been problem AFAIU. It just went unnoticed because we : have zeroed memmaps during allocation before f7f9910 ("mm: stop : zeroing memory during allocation in vmemmap") and so the above test : would simply skip these ranges as belonging to zone 0 or provided a : garbage. : : So I guess we do care for post f7f9910 kernels mostly and : therefore Fixes: f7f9910 ("mm: stop zeroing memory during : allocation in vmemmap") Link: http://lkml.kernel.org/r/20181212172712.34019-2-zaslonko@linux.ibm.com Fixes: f7f9910 ("mm: stop zeroing memory during allocation in vmemmap") Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com> Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> Suggested-by: Michal Hocko <mhocko@kernel.org> Acked-by: Michal Hocko <mhocko@suse.com> Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git 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

Original file line number	Diff line number	Diff line change
`@@ -5542,6 +5542,18 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,`
`5542`	`5542`	`cond_resched();`
`5543`	`5543`	`}`
`5544`	`5544`	`}`
	`5545`	`+#ifdef CONFIG_SPARSEMEM`
	`5546`	`+ /*`
	`5547`	`+ * If the zone does not span the rest of the section then`
	`5548`	`+ * we should at least initialize those pages. Otherwise we`
	`5549`	`+ * could blow up on a poisoned page in some paths which depend`
	`5550`	`+ * on full sections being initialized (e.g. memory hotplug).`
	`5551`	`+ */`
	`5552`	`+ while (end_pfn % PAGES_PER_SECTION) {`
	`5553`	`+ __init_single_page(pfn_to_page(end_pfn), end_pfn, zone, nid);`
	`5554`	`+ end_pfn++;`
	`5555`	`+ }`
	`5556`	`+#endif`
`5545`	`5557`	`}`
`5546`	`5558`
`5547`	`5559`	`#ifdef CONFIG_ZONE_DEVICE`