[PATCH] mm/swapfile: unuse_pte can map random data if swap read fails

[Miaohe Lin]

There is a bug in unuse_pte(): when swap page happens to be unreadable,
page filled with random data is mapped into user address space. The fix
is to check for PageUptodate and fail swapoff in case of error.

Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
 mm/swapfile.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 63c61f8b2611..e72a35de7a0f 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1795,6 +1795,10 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
 		ret = 0;
 		goto out;
 	}
+	if (unlikely(!PageUptodate(page))) {
+		ret = -EIO;
+		goto out;
+	}
 
 	dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
 	inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
-- 
2.23.0