| Message ID | 20210106084739.63318-6-songmuchun@bytedance.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix some bugs about HugeTLB code | expand |
On Wed 06-01-21 16:47:38, Muchun Song wrote: > 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. > > 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> Thanks! > --- > mm/hugetlb.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index bf02e81e3953..67200dd25b1d 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -5587,9 +5587,9 @@ bool isolate_huge_page(struct page *page, struct list_head *list) > { > 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; > } > -- > 2.11.0
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index bf02e81e3953..67200dd25b1d 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5587,9 +5587,9 @@ bool isolate_huge_page(struct page *page, struct list_head *list) { 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; }
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. 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> --- mm/hugetlb.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)