From: Mikhail Zaslonko <zaslonko@xxxxxxxxxxxxx> [ 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@xxxxxxxx: separated this change from http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@xxxxxxxxxxxxx] Link: http://lkml.kernel.org/r/20190128144506.15603-3-mhocko@xxxxxxxxxx [mhocko@xxxxxxxx: separated this change from http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@xxxxxxxxxxxxx] Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Signed-off-by: Mikhail Zaslonko <zaslonko@xxxxxxxxxxxxx> Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@xxxxxxxxx> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Tested-by: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Cc: Mikhail Gavrilov <mikhail.v.gavrilov@xxxxxxxxx> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- mm/memory_hotplug.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 39db89f3df657..c9d3a49bd4e20 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1297,6 +1297,9 @@ 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
