Re: [PATCH] kunit/overflow: Fix UB in overflow_allocation_test

[Erhard Furtner <erhard_f@mailbox.org>]

On Thu, 15 Aug 2024 01:04:31 +0100
Ivan Orlov <ivan.orlov0322@gmail.com> wrote:

> The 'device_name' array doesn't exist out of the
> 'overflow_allocation_test' function scope. However, it is being used as
> a driver name when calling 'kunit_driver_create' from
> 'kunit_device_register'. It produces the kernel panic with KASAN
> enabled.
> 
> Since this variable is used in one place only, remove it and pass the
> device name into kunit_device_register directly as an ascii string.
> 
> Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
> ---
>  lib/overflow_kunit.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/lib/overflow_kunit.c b/lib/overflow_kunit.c
> index f314a0c15a6d..2abc78367dd1 100644
> --- a/lib/overflow_kunit.c
> +++ b/lib/overflow_kunit.c
> @@ -668,7 +668,6 @@ DEFINE_TEST_ALLOC(devm_kzalloc,  devm_kfree, 1, 1, 0);
>  
>  static void overflow_allocation_test(struct kunit *test)
>  {
> -	const char device_name[] = "overflow-test";
>  	struct device *dev;
>  	int count = 0;
>  
> @@ -678,7 +677,7 @@ static void overflow_allocation_test(struct kunit *test)
>  } while (0)
>  
>  	/* Create dummy device for devm_kmalloc()-family tests. */
> -	dev = kunit_device_register(test, device_name);
> +	dev = kunit_device_register(test, "overflow-test");
>  	KUNIT_ASSERT_FALSE_MSG(test, IS_ERR(dev),
>  			       "Cannot register test device\n");
>  
> -- 
> 2.34.1

Thanks Ivan!

I can confirm that your patch fixes the KASAN hit on ppc32 when the overflow_kunit test is built as a module and modprobed later.

Regards,
Erhard