On 3/1/21 4:40 AM, gregkh@linuxfoundation.org wrote:
The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
From 9931c7726df39e891b45d118cdcad45666d7551c Mon Sep 17 00:00:00 2001
From: Mike Kravetz mike.kravetz@oracle.com Date: Mon, 1 Mar 2021 18:12:38 -0800 Subject: [PATCH] hugetlb: fix update_and_free_page contig page struct assumption MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
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-A1A1628F4AF2@nvidia...
Link: https://lkml.kernel.org/r/20210217184926.33567-1-mike.kravetz@oracle.com Fixes: 944d9fec8d7a ("hugetlb: add support for gigantic page allocation at runtime") Signed-off-by: Zi Yan ziy@nvidia.com Signed-off-by: Mike Kravetz mike.kravetz@oracle.com Cc: Zi Yan ziy@nvidia.com Cc: Davidlohr Bueso dbueso@suse.de Cc: "Kirill A . Shutemov" kirill.shutemov@linux.intel.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: Matthew Wilcox willy@infradead.org Cc: Oscar Salvador osalvador@suse.de Cc: Joao Martins joao.m.martins@oracle.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Mike Kravetz mike.kravetz@oracle.com --- mm/hugetlb.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 5a16d892c891..a73c9fbbeb6f 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1168,14 +1168,16 @@ static inline int alloc_fresh_gigantic_page(struct hstate *h, 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);