[PATCH 5.19 0727/1157] lib/test_hmm: avoid accessing uninitialized pages

Greg Kroah-Hartman
2022-08-16T00:22:43Z

From: Miaohe Lin <linmiaohe@huawei.com>

[ Upstream commit ed913b055a74b723976f8e885a3395162a0371e6 ]

If make_device_exclusive_range() fails or returns pages marked for
exclusive access less than required, remaining fields of pages will left
uninitialized. So dmirror_atomic_map() will access those yet
uninitialized fields of pages. To fix it, do dmirror_atomic_map() iff all
pages are marked for exclusive access (we will break if mapped is less
than required anyway) so we won't access those uninitialized fields of
pages.

Link: https://lkml.kernel.org/r/20220609130835.35110-1-linmiaohe@huawei.com
Fixes: b659baea7546 ("mm: selftests for exclusive device memory")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
lib/test_hmm.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index cfe632047839..f2c3015c5c82 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -732,7 +732,7 @@ static int dmirror_exclusive(struct dmirror *dmirror,

mmap_read_lock(mm);
for (addr = start; addr < end; addr = next) {
- unsigned long mapped;
+ unsigned long mapped = 0;
int i;

if (end < addr + (ARRAY_SIZE(pages) << PAGE_SHIFT))
@@ -741,7 +741,13 @@ static int dmirror_exclusive(struct dmirror *dmirror,
next = addr + (ARRAY_SIZE(pages) << PAGE_SHIFT);

ret = make_device_exclusive_range(mm, addr, next, pages, NULL);
- mapped = dmirror_atomic_map(addr, next, pages, dmirror);
+ /*
+ * Do dmirror_atomic_map() iff all pages are marked for
+ * exclusive access to avoid accessing uninitialized
+ * fields of pages.
+ */
+ if (ret == (next - addr) >> PAGE_SHIFT)
+ mapped = dmirror_atomic_map(addr, next, pages, dmirror);
for (i = 0; i < ret; i++) {
if (pages[i]) {
unlock_page(pages[i]);
--
2.35.1