This is a note to let you know that I've just added the patch titled hugetlb: fix update_and_free_page contig page struct assumption to the 5.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: hugetlb-fix-update_and_free_page-contig-page-struct-assumption.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From dbfee5aee7e54f83d96ceb8e3e80717fac62ad63 Mon Sep 17 00:00:00 2001 From: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Date: Wed, 24 Feb 2021 12:07:50 -0800 Subject: 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 From: Mike Kravetz <mike.kravetz@xxxxxxxxxx> 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@xxxxxxxxxx/ Link: https://lkml.kernel.org/r/20210217184926.33567-1-mike.kravetz@xxxxxxxxxx Fixes: 944d9fec8d7a ("hugetlb: add support for gigantic page allocation at runtime") Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Zi Yan <ziy@xxxxxxxxxx> Cc: Davidlohr Bueso <dbueso@xxxxxxx> Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxx> Cc: Joao Martins <joao.m.martins@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/hugetlb.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1312,14 +1312,16 @@ static inline void destroy_compound_giga 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_runtime_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); Patches currently in stable-queue which might be from mike.kravetz@xxxxxxxxxx are queue-5.11/hugetlb-fix-copy_huge_page_from_user-contig-page-struct-assumption.patch queue-5.11/mm-hugetlb-fix-potential-double-free-in-hugetlb_regi.patch queue-5.11/hugetlb-fix-update_and_free_page-contig-page-struct-assumption.patch queue-5.11/mm-hugetlb-suppress-wrong-warning-info-when-alloc-gi.patch queue-5.11/mm-rmap-fix-potential-pte_unmap-on-an-not-mapped-pte.patch