[070/227] mm: shmem: fix missing cache flush in shmem_mfill_atomic_pte()

Commit Message

Andrew Morton March 22, 2022, 9:42 p.m. UTC

From: Muchun Song <[e-mail]>
Subject: 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/[e-mail]
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 <[e-mail]>
Reviewed-by: Mike Kravetz <[e-mail]>
Cc: Axel Rasmussen <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Fam Zheng <[e-mail]>
Cc: Kirill A. Shutemov <[e-mail]>
Cc: Lars Persson <[e-mail]>
Cc: Peter Xu <[e-mail]>
Cc: Xiongchun Duan <[e-mail]>
Cc: Zi Yan <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/shmem.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Patch

--- a/mm/shmem.c~mm-shmem-fix-missing-cache-flush-in-shmem_mfill_atomic_pte
+++ a/mm/shmem.c
@@ -2364,8 +2364,10 @@  int shmem_mfill_atomic_pte(struct mm_str
 				/* 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;