Re: [PATCH] ext4: Fix potential null dereference in ext4 test

[Kemeng Shi]

on 3/7/2025 7:54 PM, Charles Han wrote:
> kunit_kzalloc() may return a NULL pointer, dereferencing it without
> NULL check may lead to NULL dereference.
> Add a NULL check for test_state
> 
> Fixes: b7098e1fa7bc ("ext4: Add unit test for mb_free_blocks")
> Fixes: ac96b56a2fbd ("ext4: Add unit test for mb_mark_used")
> Signed-off-by: Charles Han <hanchunchao@xxxxxxxxxx>
> ---
>  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);
> 
Good catch, looks good to me.

Reviewed-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>