From: Mike Kravetz <mike.krav...@oracle.com> commit dbfee5aee7e54f83d96ceb8e3e80717fac62ad63 upstream.
page structs are not guaranteed to be contiguous for gigantic pages. The routine update_and_free_page can encounter a gigantic page, yet it assumes page structs are contiguous when setting page flags in subpages. If update_and_free_page encounters non-contiguous page structs, we can see “BUG: Bad page state in process …” errors. Non-contiguous page structs are generally not an issue. However, they can exist with a specific kernel configuration and hotplug operations. For example: Configure the kernel with CONFIG_SPARSEMEM and !CONFIG_SPARSEMEM_VMEMMAP. Then, hotplug add memory for the area where the gigantic page will be allocated. Zi Yan outlined steps to reproduce here [1]. [1] https://lore.kernel.org/linux-mm/16f7c58b-4d79-41c5-9b64-a1a1628f4...@nvidia.com/ Link: https://lkml.kernel.org/r/20210217184926.33567-1-mike.krav...@oracle.com Fixes: 944d9fec8d7a ("hugetlb: add support for gigantic page allocation at runtime") Signed-off-by: Zi Yan <z...@nvidia.com> Signed-off-by: Mike Kravetz <mike.krav...@oracle.com> Cc: Zi Yan <z...@nvidia.com> Cc: Davidlohr Bueso <dbu...@suse.de> Cc: "Kirill A . Shutemov" <kirill.shute...@linux.intel.com> Cc: Andrea Arcangeli <aarca...@redhat.com> Cc: Matthew Wilcox <wi...@infradead.org> Cc: Oscar Salvador <osalva...@suse.de> Cc: Joao Martins <joao.m.mart...@oracle.com> Cc: <sta...@vger.kernel.org> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> Signed-off-by: Mike Kravetz <mike.krav...@oracle.com> --- mm/hugetlb.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1185,14 +1185,16 @@ static inline int alloc_fresh_gigantic_p static void update_and_free_page(struct hstate *h, struct page *page) { int i; + struct page *subpage = page; if (hstate_is_gigantic(h) && !gigantic_page_supported()) return; h->nr_huge_pages--; h->nr_huge_pages_node[page_to_nid(page)]--; - for (i = 0; i < pages_per_huge_page(h); i++) { - page[i].flags &= ~(1 << PG_locked | 1 << PG_error | + for (i = 0; i < pages_per_huge_page(h); + i++, subpage = mem_map_next(subpage, page, i)) { + subpage->flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced | 1 << PG_dirty | 1 << PG_active | 1 << PG_private | 1 << PG_writeback);
