4.19-stable review patch. If anyone has any objections, please let me know.
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[ 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 34cde04f346d..ff93a57e1694 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;