[PATCH] damon: vaddr-test: fix a missing check on list iterator

Xiaomeng Tong
2022-03-27T08:03:56Z

The bug is here:
KUNIT_EXPECT_EQ(test, r->ar.start, start + i * expected_width);
KUNIT_EXPECT_EQ(test, r->ar.end, end);

For the damon_for_each_region(), just like list_for_each_entry(),
the list iterator 'drm_crtc' will point to a bogus position
containing HEAD if the list is empty or no element is found.
This case must be checked before any use of the iterator,
otherwise it will lead to a invalid memory access.

To fix this bug, just mov two KUNIT_EXPECT_EQ() into the loop
when found.

Cc: stable@vger.kernel.org
Fixes: 044cd9750fe01 ("mm/damon/vaddr-test: split a test function having >1024 bytes frame size")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
---
mm/damon/vaddr-test.h | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/damon/vaddr-test.h b/mm/damon/vaddr-test.h
index 6a1b9272ea12..98b7a9f54b35 100644
--- a/mm/damon/vaddr-test.h
+++ b/mm/damon/vaddr-test.h
@@ -281,14 +281,16 @@ static void damon_test_split_evenly_succ(struct kunit *test,
KUNIT_EXPECT_EQ(test, damon_nr_regions(t), nr_pieces);

damon_for_each_region(r, t) {
- if (i == nr_pieces - 1)
+ if (i == nr_pieces - 1) {
+ KUNIT_EXPECT_EQ(test,
+ r->ar.start, start + i * expected_width);
+ KUNIT_EXPECT_EQ(test, r->ar.end, end);
break;
+ }
KUNIT_EXPECT_EQ(test,
r->ar.start, start + i++ * expected_width);
KUNIT_EXPECT_EQ(test, r->ar.end, start + i * expected_width);
}
- KUNIT_EXPECT_EQ(test, r->ar.start, start + i * expected_width);
- KUNIT_EXPECT_EQ(test, r->ar.end, end);
damon_free_target(t);
}

--
2.17.1