linux-kernel - [PATCH] ext4: Fix potential NULL pointer dereferences in test_mb_mark_used() and test_mb_free

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Message-Id: <20250305124012.28500-1-qasdev00@gmail.com>
Date: Wed,  5 Mar 2025 12:40:12 +0000
From: Qasim Ijaz <qasdev00@...il.com>
To: adilger.kernel@...ger.ca,
	tytso@....edu
Cc: linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: [PATCH] ext4: Fix potential NULL pointer dereferences in test_mb_mark_used() and test_mb_free_blocks()

test_mb_mark_used() and test_mb_free_blocks() call kunit_kzalloc() to 
allocate memory, however both fail to ensure that the allocations 
succeeded. If kunit_kzalloc() returns NULL, then dereferencing the 
corresponding pointer without checking for NULL will lead to 
a NULL pointer dereference.

To fix this call KUNIT_ASSERT_NOT_ERR_OR_NULL() to ensure 
the allocation succeeded.

Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
Fixes: ac96b56a2fbd ("ext4: Add unit test for mb_mark_used")
Fixes: b7098e1fa7bc ("ext4: Add unit test for mb_free_blocks")
Cc: stable@...r.kernel.org
---
 fs/ext4/mballoc-test.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/ext4/mballoc-test.c b/fs/ext4/mballoc-test.c
index bb2a223b207c..d634c12f1984 100644
--- a/fs/ext4/mballoc-test.c
+++ b/fs/ext4/mballoc-test.c
@@ -796,6 +796,7 @@ static void test_mb_mark_used(struct kunit *test)
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buddy);
 	grp = kunit_kzalloc(test, offsetof(struct ext4_group_info,
 				bb_counters[MB_NUM_ORDERS(sb)]), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, grp);
 
 	ret = ext4_mb_load_buddy(sb, TEST_GOAL_GROUP, &e4b);
 	KUNIT_ASSERT_EQ(test, ret, 0);
@@ -860,6 +861,7 @@ static void test_mb_free_blocks(struct kunit *test)
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buddy);
 	grp = kunit_kzalloc(test, offsetof(struct ext4_group_info,
 				bb_counters[MB_NUM_ORDERS(sb)]), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, grp);
 
 	ret = ext4_mb_load_buddy(sb, TEST_GOAL_GROUP, &e4b);
 	KUNIT_ASSERT_EQ(test, ret, 0);
-- 
2.39.5