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From:   Miaohe Lin <linmiaohe@huawei.com>
To:     <akpm@linux-foundation.org>
CC:     <jglisse@redhat.com>, <shy828301@gmail.com>, <aquini@redhat.com>,
        <david@redhat.com>, <apopple@nvidia.com>,
        <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
        <linmiaohe@huawei.com>
Subject: [PATCH v2 3/5] mm/migrate.c: fix potential indeterminate pte entry in migrate_vma_insert_page()
Date:   Tue, 23 Mar 2021 09:54:03 -0400
Message-ID: <20210323135405.65059-4-linmiaohe@huawei.com>
In-Reply-To: <20210323135405.65059-1-linmiaohe@huawei.com>
References: <20210323135405.65059-1-linmiaohe@huawei.com>
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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.

Fixes: df6ad69838fc ("mm/device-public-memory: device memory cache coherent with CPU")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 mm/migrate.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/migrate.c b/mm/migrate.c
index 97da1fabdf72..d372be3da9b2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2972,6 +2972,13 @@ 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);
-- 
2.19.1