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

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Message-ID: <92d0e215879f153331084722375dda57517d49f4.camel@linux.intel.com>
Date: Mon, 17 Mar 2025 12:05:15 -0700
From: Tim Chen <tim.c.chen@...ux.intel.com>
To: Qasim Ijaz <qasdev00@...il.com>, adilger.kernel@...ger.ca,
 tytso@....edu,  shikemeng@...weicloud.com
Cc: linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org
Subject: Re: [PATCH RESEND] ext4: Fix potential NULL pointer dereferences in
 test_mb_mark_used() and test_mb_free_blocks()

On Thu, 2025-03-13 at 00:00 +0000, Qasim Ijaz wrote:
> 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.
> 

Reviewed-by: Tim Chen <tim.c.chen@...ux.intel.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
> Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
> ---
>  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);