linux-kernel - Re: [PATCH mm 3/3] kasan: migrate workqueue

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Date:   Tue, 27 Sep 2022 15:17:10 +0200
From:   Marco Elver <elver@...gle.com>
To:     andrey.konovalov@...ux.dev
Cc:     Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev@...glegroups.com,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH mm 3/3] kasan: migrate workqueue_uaf test to kunit

On Sat, Sep 24, 2022 at 08:31PM +0200, andrey.konovalov@...ux.dev wrote:
> From: Andrey Konovalov <andreyknvl@...gle.com>
> 
> Migrate the workqueue_uaf test to the KUnit framework.
> 
> Initially, this test was intended to check that Generic KASAN prints
> auxiliary stack traces for workqueues. Nevertheless, the test is enabled
> for all modes to make that KASAN reports bad accesses in the tested
> scenario.
> 
> The presence of auxiliary stack traces for the Generic mode needs to be
> inspected manually.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>

Reviewed-by: Marco Elver <elver@...gle.com>

> ---
>  mm/kasan/kasan_test.c        | 40 +++++++++++++++++++++++++++++-------
>  mm/kasan/kasan_test_module.c | 30 ---------------------------
>  2 files changed, 33 insertions(+), 37 deletions(-)
> 
> diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
> index 005776325e20..71cb402c404f 100644
> --- a/mm/kasan/kasan_test.c
> +++ b/mm/kasan/kasan_test.c
> @@ -1134,6 +1134,14 @@ static void kmalloc_double_kzfree(struct kunit *test)
>  	KUNIT_EXPECT_KASAN_FAIL(test, kfree_sensitive(ptr));
>  }
>  
> +/*
> + * The two tests below check that Generic KASAN prints auxiliary stack traces
> + * for RCU callbacks and workqueues. The reports need to be inspected manually.
> + *
> + * These tests are still enabled for other KASAN modes to make sure that all
> + * modes report bad accesses in tested scenarios.
> + */
> +
>  static struct kasan_rcu_info {
>  	int i;
>  	struct rcu_head rcu;
> @@ -1148,13 +1156,6 @@ static void rcu_uaf_reclaim(struct rcu_head *rp)
>  	((volatile struct kasan_rcu_info *)fp)->i;
>  }
>  
> -/*
> - * Check that Generic KASAN prints auxiliary stack traces for RCU callbacks.
> - * The report needs to be inspected manually.
> - *
> - * This test is still enabled for other KASAN modes to make sure that all modes
> - * report bad accesses in tested scenarios.
> - */
>  static void rcu_uaf(struct kunit *test)
>  {
>  	struct kasan_rcu_info *ptr;
> @@ -1170,6 +1171,30 @@ static void rcu_uaf(struct kunit *test)
>  		rcu_barrier());
>  }
>  
> +static void workqueue_uaf_work(struct work_struct *work)
> +{
> +	kfree(work);
> +}
> +
> +static void workqueue_uaf(struct kunit *test)
> +{
> +	struct workqueue_struct *workqueue;
> +	struct work_struct *work;
> +
> +	workqueue = create_workqueue("kasan_workqueue_test");
> +	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, workqueue);
> +
> +	work = kmalloc(sizeof(struct work_struct), GFP_KERNEL);
> +	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, work);
> +
> +	INIT_WORK(work, workqueue_uaf_work);
> +	queue_work(workqueue, work);
> +	destroy_workqueue(workqueue);
> +
> +	KUNIT_EXPECT_KASAN_FAIL(test,
> +		((volatile struct work_struct *)work)->data);
> +}
> +
>  static void vmalloc_helpers_tags(struct kunit *test)
>  {
>  	void *ptr;
> @@ -1502,6 +1527,7 @@ static struct kunit_case kasan_kunit_test_cases[] = {
>  	KUNIT_CASE(kasan_bitops_tags),
>  	KUNIT_CASE(kmalloc_double_kzfree),
>  	KUNIT_CASE(rcu_uaf),
> +	KUNIT_CASE(workqueue_uaf),
>  	KUNIT_CASE(vmalloc_helpers_tags),
>  	KUNIT_CASE(vmalloc_oob),
>  	KUNIT_CASE(vmap_tags),
> diff --git a/mm/kasan/kasan_test_module.c b/mm/kasan/kasan_test_module.c
> index 4688cbcd722d..7be7bed456ef 100644
> --- a/mm/kasan/kasan_test_module.c
> +++ b/mm/kasan/kasan_test_module.c
> @@ -62,35 +62,6 @@ static noinline void __init copy_user_test(void)
>  	kfree(kmem);
>  }
>  
> -static noinline void __init kasan_workqueue_work(struct work_struct *work)
> -{
> -	kfree(work);
> -}
> -
> -static noinline void __init kasan_workqueue_uaf(void)
> -{
> -	struct workqueue_struct *workqueue;
> -	struct work_struct *work;
> -
> -	workqueue = create_workqueue("kasan_wq_test");
> -	if (!workqueue) {
> -		pr_err("Allocation failed\n");
> -		return;
> -	}
> -	work = kmalloc(sizeof(struct work_struct), GFP_KERNEL);
> -	if (!work) {
> -		pr_err("Allocation failed\n");
> -		return;
> -	}
> -
> -	INIT_WORK(work, kasan_workqueue_work);
> -	queue_work(workqueue, work);
> -	destroy_workqueue(workqueue);
> -
> -	pr_info("use-after-free on workqueue\n");
> -	((volatile struct work_struct *)work)->data;
> -}
> -
>  static int __init test_kasan_module_init(void)
>  {
>  	/*
> @@ -101,7 +72,6 @@ static int __init test_kasan_module_init(void)
>  	bool multishot = kasan_save_enable_multi_shot();
>  
>  	copy_user_test();
> -	kasan_workqueue_uaf();
>  
>  	kasan_restore_multi_shot(multishot);
>  	return -EAGAIN;
> -- 
> 2.25.1