mm/migrate.c: fix potential indeterminate pte entry in migrate_vma_insert_page()

[ 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@huawei.com
Fixes: df6ad69838fc ("mm/device-public-memory: device memory cache coherent with CPU")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/mm/migrate.c b/mm/migrate.c
index 9d7ca1b..7982256 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2914,6 +2914,13 @@ 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);