4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> [ Upstream commit f073bdc51771f5a5c7a8d1191bfc3ae371d44de7 ] The VM_BUG_ON() check in move_freepages() checks whether the node id of a page matches the node id of its zone. However, it does this before having checked whether the struct page pointer refers to a valid struct page to begin with. This is guaranteed in most cases, but may not be the case if CONFIG_HOLES_IN_ZONE=y. So reorder the VM_BUG_ON() with the pfn_valid_within() check. Link: http://lkml.kernel.org/r/1481706707-6211-2-git-send-email-ard.biesheuvel@xxxxxxxxxx Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> Acked-by: Will Deacon <will.deacon@xxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Hanjun Guo <hanjun.guo@xxxxxxxxxx> Cc: Yisheng Xie <xieyisheng1@xxxxxxxxxx> Cc: Robert Richter <rrichter@xxxxxxxxxx> Cc: James Morse <james.morse@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1875,14 +1875,14 @@ int move_freepages(struct zone *zone, #endif for (page = start_page; page <= end_page;) { - /* Make sure we are not inadvertently changing nodes */ - VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page); - if (!pfn_valid_within(page_to_pfn(page))) { page++; continue; } + /* Make sure we are not inadvertently changing nodes */ + VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page); + if (!PageBuddy(page)) { page++; continue;