[PATCH 5.4 082/141] mm/migrate.c: fix potential indeterminate pte entry in migrate_vma_insert_page()

[Greg Kroah-Hartman]

From: Miaohe Lin <linmiaohe@xxxxxxxxxx>

[ Upstream commit 34f5e9b9d1990d286199084efa752530ee3d8297 ]

If the zone device page does not belong to un-addressable device memory,
the variable entry will be uninitialized and lead to indeterminate pte
entry ultimately.  Fix this unexpected case and warn about it.

Link: https://lkml.kernel.org/r/20210325131524.48181-4-linmiaohe@xxxxxxxxxx
Fixes: df6ad69838fc ("mm/device-public-memory: device memory cache coherent with CPU")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: Rafael Aquini <aquini@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 mm/migrate.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/migrate.c b/mm/migrate.c
index c4c313e47f12..00bbe57c1ce2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2771,6 +2771,13 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
 
 			swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
 			entry = swp_entry_to_pte(swp_entry);
+		} else {
+			/*
+			 * For now we only support migrating to un-addressable
+			 * device memory.
+			 */
+			pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
+			goto abort;
 		}
 	} else {
 		entry = mk_pte(page, vma->vm_page_prot);
-- 
2.30.2