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authorQian Cai <cai@lca.pw>2019-10-18 20:19:29 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-10-19 06:32:31 -0400
commita26ee565b6cd8dc2bf15ff6aa70bbb28f928b773 (patch)
treed5e2c48a19d08cc08538314ae2a8a212d606a1e5
parentca210ba32ef7537b02731bfe255ed8eb1e4e2b59 (diff)
mm/page_owner: don't access uninitialized memmaps when reading /proc/pagetypeinfo
Uninitialized memmaps contain garbage and in the worst case trigger kernel BUGs, especially with CONFIG_PAGE_POISONING. They should not get touched. For example, when not onlining a memory block that is spanned by a zone and reading /proc/pagetypeinfo with CONFIG_DEBUG_VM_PGFLAGS and CONFIG_PAGE_POISONING, we can trigger a kernel BUG: :/# echo 1 > /sys/devices/system/memory/memory40/online :/# echo 1 > /sys/devices/system/memory/memory42/online :/# cat /proc/pagetypeinfo > test.file page:fffff2c585200000 is uninitialized and poisoned raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) There is not page extension available. ------------[ cut here ]------------ kernel BUG at include/linux/mm.h:1107! invalid opcode: 0000 [#1] SMP NOPTI Please note that this change does not affect ZONE_DEVICE, because pagetypeinfo_showmixedcount_print() is called from mm/vmstat.c:pagetypeinfo_showmixedcount() only for populated zones, and ZONE_DEVICE is never populated (zone->present_pages always 0). [david@redhat.com: move check to outer loop, add comment, rephrase description] Link: http://lkml.kernel.org/r/20191011140638.8160-1-david@redhat.com Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") # visible after d0dc12e86b319 Signed-off-by: Qian Cai <cai@lca.pw> Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> Cc: Miles Chen <miles.chen@mediatek.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Qian Cai <cai@lca.pw> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: <stable@vger.kernel.org> [4.13+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/page_owner.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/mm/page_owner.c b/mm/page_owner.c
index e327bcd0380e..18ecde9f45b2 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -271,7 +271,8 @@ void pagetypeinfo_showmixedcount_print(struct seq_file *m,
* not matter as the mixed block count will still be correct
*/
for (; pfn < end_pfn; ) {
- if (!pfn_valid(pfn)) {
+ page = pfn_to_online_page(pfn);
+ if (!page) {
pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
continue;
}
@@ -279,13 +280,13 @@ void pagetypeinfo_showmixedcount_print(struct seq_file *m,
block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
block_end_pfn = min(block_end_pfn, end_pfn);
- page = pfn_to_page(pfn);
pageblock_mt = get_pageblock_migratetype(page);
for (; pfn < block_end_pfn; pfn++) {
if (!pfn_valid_within(pfn))
continue;
+ /* The pageblock is online, no need to recheck. */
page = pfn_to_page(pfn);
if (page_zone(page) != zone)