The patch below does not apply to the 5.15-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.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 348923665a0e50ad9fc0b3bb8127d3cb976691cc Mon Sep 17 00:00:00 2001 From: Muchun Song songmuchun@bytedance.com Date: Tue, 22 Mar 2022 14:42:02 -0700 Subject: [PATCH] mm: hugetlb: fix missing cache flush in hugetlb_mcopy_atomic_pte()

folio_copy() will copy the data from one page to the target page, then the target page will be mapped to the user space address, which might have an alias issue with the kernel address used to copy the data from the page to. There are 2 ways to fix this issue.

1) insert flush_dcache_page() after folio_copy().

2) replace folio_copy() with copy_user_huge_page() which already considers the cache maintenance.

We chose 2) way to fix the issue since architectures can optimize this situation. It is also make backports easier.

Link: https://lkml.kernel.org/r/20220210123058.79206-5-songmuchun@bytedance.com Fixes: 8cc5fcbb5be8 ("mm, hugetlb: fix racy resv_huge_pages underflow on UFFDIO_COPY") Signed-off-by: Muchun Song songmuchun@bytedance.com Reviewed-by: Mike Kravetz mike.kravetz@oracle.com Cc: Axel Rasmussen axelrasmussen@google.com Cc: David Rientjes rientjes@google.com Cc: Fam Zheng fam.zheng@bytedance.com Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Lars Persson lars.persson@axis.com Cc: Peter Xu peterx@redhat.com Cc: Xiongchun Duan duanxiongchun@bytedance.com Cc: Zi Yan ziy@nvidia.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org

diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a404af0b49a0..3d450f802823 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5816,7 +5816,8 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, *pagep = NULL; goto out; } - folio_copy(page_folio(page), page_folio(*pagep)); + copy_user_huge_page(page, *pagep, dst_addr, dst_vma, + pages_per_huge_page(h)); put_page(*pagep); *pagep = NULL; }