mm: shmem: fix missing cache flush in shmem_mfill_atomic_pte()

userfaultfd calls shmem_mfill_atomic_pte() which does not do any cache
flushing for the target page.  Then the target page will be mapped to
the user space with a different address (user address), which might have
an alias issue with the kernel address used to copy the data from the
user to.  Insert flush_dcache_page() in non-zero-page case.  And replace
clear_highpage() with clear_user_highpage() which already considers the
cache maintenance.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 8d1039634206 ("userfaultfd: shmem: add shmem_mfill_zeropage_pte for userfaultfd support")
Fixes: 4c27fe4c4c84 ("userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support")
Signed-off-by: Muchun Song <[email protected]>
Reviewed-by: Mike Kravetz <[email protected]>
Cc: Axel Rasmussen <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Fam Zheng <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Lars Persson <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Xiongchun Duan <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 3 insertions, 1 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index f21eb0ef8ae0..01fd227b6947 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2364,8 +2364,10 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
 				/* don't free the page */
 				goto out_unacct_blocks;
 			}
+
+			flush_dcache_page(page);
 		} else {		/* ZEROPAGE */
-			clear_highpage(page);
+			clear_user_highpage(page, dst_addr);
 		}
 	} else {
 		page = *pagep;