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Subject: Re: [PATCH v4 1/3] lib/test_kasan: Add bitops tests
To:     Marco Elver <elver@google.com>, peterz@infradead.org,
        dvyukov@google.com, glider@google.com, andreyknvl@google.com,
        mark.rutland@arm.com, hpa@zytor.com
Cc:     corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        x86@kernel.org, arnd@arndb.de, jpoimboe@redhat.com,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arch@vger.kernel.org, kasan-dev@googlegroups.com
References: <20190613123028.179447-1-elver@google.com>
 <20190613123028.179447-2-elver@google.com>
From:   Andrey Ryabinin <aryabinin@virtuozzo.com>
Message-ID: <6cc5e12d-1492-d9b7-3ea7-6381407439d7@virtuozzo.com>
Date:   Thu, 13 Jun 2019 15:50:06 +0300
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On 6/13/19 3:30 PM, 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@google.com>
> Acked-by: Mark Rutland <mark.rutland@arm.com>
> ---

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>


> +static noinline void __init kasan_bitops(void)
> +{
> +	/*
> +	 * Allocate 1 more byte, which causes kzalloc to round up to 16-bytes;
> +	 * this way we do not actually corrupt other memory, in case
> +	 * instrumentation is not working as intended.

This sound like working instrumentation somehow save us from corrupting memory. In fact it doesn't,
it only reports corruption.

> +	 */
> +	long *bits = kzalloc(sizeof(*bits) + 1, GFP_KERNEL);
> +	if (!bits)
> +		return;
> +