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Subject[PATCH AUTOSEL 4.19 61/65] mm, memory_hotplug: test_pages_in_a_zone do not pass the end of zone
Date
From: Mikhail Zaslonko <zaslonko@linux.ibm.com>

[ Upstream commit 24feb47c5fa5b825efb0151f28906dfdad027e61 ]

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:
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

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]
Link: http://lkml.kernel.org/r/20190128144506.15603-3-mhocko@kernel.org

[mhocko@suse.com: separated this change from
http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com]
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Tested-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
mm/memory_hotplug.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 34cde04f346d9..ff93a57e1694c 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1299,6 +1299,9 @@ 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;
--
2.19.1
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