| Message ID | 20220208073617.70342-5-songmuchun@bytedance.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Fix some cache flush bugs | expand |
On 2/7/22 23:36, Muchun Song wrote: > 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. > > Fixes: 8cc5fcbb5be8 ("mm, hugetlb: fix racy resv_huge_pages underflow on UFFDIO_COPY") > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > --- > mm/hugetlb.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) Thanks! This will also make backports easier. Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a1baa198519a..eba7681d15d0 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5818,7 +5818,8 @@ 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; }
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. Fixes: 8cc5fcbb5be8 ("mm, hugetlb: fix racy resv_huge_pages underflow on UFFDIO_COPY") Signed-off-by: Muchun Song <songmuchun@bytedance.com> --- mm/hugetlb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)