From: Mikhail Zaslonko <zaslonko@xxxxxxxxxxxxx>
[ Upstream commit 2830bf6f05fb3e05bc4743274b806c821807a684 ]
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 f7f99100d8d9 ("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 f7f99100d8d9 kernels mostly and
: therefore Fixes: f7f99100d8d9 ("mm: stop zeroing memory during
: allocation in vmemmap")
Link: http://lkml.kernel.org/r/20181212172712.34019-2-zaslonko@xxxxxxxxxxxxx
Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap")
Signed-off-by: Mikhail Zaslonko <zaslonko@xxxxxxxxxxxxx>
Reviewed-by: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx>
Suggested-by: Michal Hocko <mhocko@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@xxxxxxxxx>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
Cc: Pasha Tatashin <Pavel.Tatashin@xxxxxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
mm/page_alloc.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 923deb33bf34..16c20d9e771f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5348,6 +5348,18 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
__init_single_pfn(pfn, zone, nid);
}
}
+#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
}
static void __meminit zone_init_free_lists(struct zone *zone)
--
2.20.1
