The 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.
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 <songmuchun@xxxxxxxxxxxxx>
---
mm/shmem.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index eb0fd9001130..2e17ec9231a2 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2371,8 +2371,10 @@ 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;
--
2.11.0
