[PATCH AUTOSEL 04/14] mm: hugetlb: fix missing cache flush in hugetlb_mcopy_atomic_pte()

Greg Kroah-Hartman
2022-04-28T15:43:09Z

From: Muchun Song <songmuchun@bytedance.com>

commit 348923665a0e50ad9fc0b3bb8127d3cb976691cc upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/hugetlb.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a1da8757cc9c..e2dc190c6725 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5820,7 +5820,8 @@ 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;
}
--
2.36.0