The patch titled Subject: mm: hugetlb: fix a race between isolating and freeing page has been added to the -mm tree. Its filename is mm-hugetlb-fix-a-race-between-isolating-and-freeing-page.patch

This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-fix-a-race-between-isol... and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-fix-a-race-between-isol...

Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated there every 3-4 working days

------------------------------------------------------ From: Muchun Song songmuchun@bytedance.com Subject: mm: hugetlb: fix a race between isolating and freeing page

There is a race between isolate_huge_page() and __free_huge_page().

CPU0: CPU1:

if (PageHuge(page)) put_page(page) __free_huge_page(page) spin_lock(&hugetlb_lock) update_and_free_page(page) set_compound_page_dtor(page, NULL_COMPOUND_DTOR) spin_unlock(&hugetlb_lock) isolate_huge_page(page) // trigger BUG_ON VM_BUG_ON_PAGE(!PageHead(page), page) spin_lock(&hugetlb_lock) page_huge_active(page) // trigger BUG_ON VM_BUG_ON_PAGE(!PageHuge(page), page) spin_unlock(&hugetlb_lock)

When we isolate a HugeTLB page on CPU0. Meanwhile, we free it to the buddy allocator on CPU1. Then, we can trigger a BUG_ON on CPU0. Because it is already freed to the buddy allocator.

Link: https://lkml.kernel.org/r/20210110124017.86750-6-songmuchun@bytedance.com Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage") Signed-off-by: Muchun Song songmuchun@bytedance.com Reviewed-by: Mike Kravetz mike.kravetz@oracle.com Acked-by: Michal Hocko mhocko@suse.com Cc: Andi Kleen ak@linux.intel.com Cc: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/hugetlb.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlb-fix-a-race-between-isolating-and-freeing-page +++ a/mm/hugetlb.c @@ -5581,9 +5581,9 @@ bool isolate_huge_page(struct page *page { bool ret = true;

- VM_BUG_ON_PAGE(!PageHead(page), page); spin_lock(&hugetlb_lock); - if (!page_huge_active(page) || !get_page_unless_zero(page)) { + if (!PageHeadHuge(page) || !page_huge_active(page) || + !get_page_unless_zero(page)) { ret = false; goto unlock; } _

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-hugetlbfs-fix-cannot-migrate-the-fallocated-hugetlb-page.patch mm-hugetlb-fix-a-race-between-freeing-and-dissolving-the-page.patch mm-hugetlb-fix-a-race-between-isolating-and-freeing-page.patch mm-hugetlb-remove-vm_bug_on_page-from-page_huge_active.patch mm-memcontrol-optimize-per-lruvec-stats-counter-memory-usage.patch mm-memcontrol-fix-nr_anon_thps-accounting-in-charge-moving.patch mm-memcontrol-convert-nr_anon_thps-account-to-pages.patch mm-memcontrol-convert-nr_file_thps-account-to-pages.patch mm-memcontrol-convert-nr_shmem_thps-account-to-pages.patch mm-memcontrol-convert-nr_shmem_pmdmapped-account-to-pages.patch mm-memcontrol-convert-nr_file_pmdmapped-account-to-pages.patch mm-memcontrol-make-the-slab-calculation-consistent.patch mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one.patch mm-hugetlb-add-return-eagain-for-dissolve_free_huge_page.patch