linux-kernel - Re: [PATCH v2 1/3] lib/test

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Date:   Wed, 29 May 2019 16:15:07 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Marco Elver <elver@...gle.com>
Cc:     peterz@...radead.org, aryabinin@...tuozzo.com, dvyukov@...gle.com,
        glider@...gle.com, andreyknvl@...gle.com, corbet@....net,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, arnd@...db.de, jpoimboe@...hat.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, kasan-dev@...glegroups.com
Subject: Re: [PATCH v2 1/3] lib/test_kasan: Add bitops tests

On Wed, May 29, 2019 at 04:14:59PM +0200, Marco Elver wrote:
> This adds bitops tests to the test_kasan module. In a follow-up patch,
> support for bitops instrumentation will be added.
> 
> Signed-off-by: Marco Elver <elver@...gle.com>
> ---
> Changes in v2:
> * Use BITS_PER_LONG.
> * Use heap allocated memory for test, as newer compilers (correctly)
>   warn on OOB stack access.
> ---
>  lib/test_kasan.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 72 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index 7de2702621dc..6562df0ca30d 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -11,16 +11,17 @@
>  
>  #define pr_fmt(fmt) "kasan test: %s " fmt, __func__
>  
> +#include <linux/bitops.h>
>  #include <linux/delay.h>
> +#include <linux/kasan.h>
>  #include <linux/kernel.h>
> -#include <linux/mman.h>
>  #include <linux/mm.h>
> +#include <linux/mman.h>
> +#include <linux/module.h>
>  #include <linux/printk.h>
>  #include <linux/slab.h>
>  #include <linux/string.h>
>  #include <linux/uaccess.h>
> -#include <linux/module.h>
> -#include <linux/kasan.h>
>  
>  /*
>   * Note: test functions are marked noinline so that their names appear in
> @@ -623,6 +624,73 @@ static noinline void __init kasan_strings(void)
>  	strnlen(ptr, 1);
>  }
>  
> +static noinline void __init kasan_bitops(void)
> +{
> +	long *bits = kmalloc(sizeof(long), GFP_KERNEL | __GFP_ZERO);

Trivial nit, but this can/should be:

	long *bits = kzalloc(sizeof(*bits), GFP_KERNEL);


... which is the usual style for sizeof() to keep the LHS and RHS types
the same, and using kzalloc avoids the need to explicitly pass
__GFP_ZERO.

Otherwise, this looks good to me.

> +	if (!bits)
> +		return;
> +
> +	pr_info("within-bounds in set_bit");
> +	set_bit(0, bits);
> +
> +	pr_info("within-bounds in set_bit");
> +	set_bit(BITS_PER_LONG - 1, bits);
> +
> +	pr_info("out-of-bounds in set_bit\n");
> +	set_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in __set_bit\n");
> +	__set_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in clear_bit\n");
> +	clear_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in __clear_bit\n");
> +	__clear_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in clear_bit_unlock\n");
> +	clear_bit_unlock(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in __clear_bit_unlock\n");
> +	__clear_bit_unlock(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in change_bit\n");
> +	change_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in __change_bit\n");
> +	__change_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in test_and_set_bit\n");
> +	test_and_set_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in __test_and_set_bit\n");
> +	__test_and_set_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in test_and_set_bit_lock\n");
> +	test_and_set_bit_lock(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in test_and_clear_bit\n");
> +	test_and_clear_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in __test_and_clear_bit\n");
> +	__test_and_clear_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in test_and_change_bit\n");
> +	test_and_change_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in __test_and_change_bit\n");
> +	__test_and_change_bit(BITS_PER_LONG, bits);
> +
> +	pr_info("out-of-bounds in test_bit\n");
> +	(void)test_bit(BITS_PER_LONG, bits);
> +
> +#if defined(clear_bit_unlock_is_negative_byte)
> +	pr_info("out-of-bounds in clear_bit_unlock_is_negative_byte\n");
> +	clear_bit_unlock_is_negative_byte(BITS_PER_LONG, bits);
> +#endif
> +	kfree(bits);
> +}
> +
>  static int __init kmalloc_tests_init(void)
>  {
>  	/*
> @@ -664,6 +732,7 @@ static int __init kmalloc_tests_init(void)
>  	kasan_memchr();
>  	kasan_memcmp();
>  	kasan_strings();
> +	kasan_bitops();
>  
>  	kasan_restore_multi_shot(multishot);
>  
> -- 
> 2.22.0.rc1.257.g3120a18244-goog
>