4.20-stable review patch. If anyone has any objections, please let me know.
------------------ [ 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. [mho...@suse.com: separated this change from http://lkml.kernel.org/r/20181105150401.97287-2-zaslo...@linux.ibm.com] Link: http://lkml.kernel.org/r/20190128144506.15603-3-mho...@kernel.org [mho...@suse.com: separated this change from http://lkml.kernel.org/r/20181105150401.97287-2-zaslo...@linux.ibm.com] Signed-off-by: Michal Hocko <mho...@suse.com> Signed-off-by: Mikhail Zaslonko <zaslo...@linux.ibm.com> Tested-by: Mikhail Gavrilov <mikhail.v.gavri...@gmail.com> Reviewed-by: Oscar Salvador <osalva...@suse.de> Tested-by: Gerald Schaefer <gerald.schae...@de.ibm.com> Cc: Heiko Carstens <heiko.carst...@de.ibm.com> Cc: Martin Schwidefsky <schwidef...@de.ibm.com> Cc: Mikhail Gavrilov <mikhail.v.gavri...@gmail.com> Cc: Pavel Tatashin <pasha.tatas...@soleen.com> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Sasha Levin <sas...@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 5ce0d929ff48..488aa11495d2 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1275,6 +1275,9 @@ 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
