linux-kernel - Re: [PATCH 1/2] test_sysctl: add tests for >32-bit values written to 32-bit integers

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Message-ID: <20190206195202.GF11489@garbanzo.do-not-panic.com>
Date:   Wed, 6 Feb 2019 11:52:02 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Zev Weiss <zev@...ilderbeest.net>
Cc:     Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, Shuah Khan <shuah@...nel.org>,
        linux-kselftest@...r.kernel.org, akpm@...ux-foundation.org,
        yzaikin@...gle.com, brendanhiggins@...gle.com
Subject: Re: [PATCH 1/2] test_sysctl: add tests for >32-bit values written to
 32-bit integers

Thanks for the patches, please include akpm@...ux-foundation.org in the
future, as we can merge the changes through Andrew as well.

Also please Cc yzaikin@...gle.com, brendanhiggins@...gle.com in follow
ups for now.  They are looking at the sysctl testing code as well.

Some feedback below:

In-Reply-To: <20181227111231.12912-2-zev@...ilderbeest.net>

On Thu, Dec 27, 2018 at 05:12:29AM -0600, Zev Weiss wrote:
> +run_wideint_tests()
> +{
> +	# check negative and positive 64-bit values, with and without
> +	# bits set in the lower 31, and with and without bit 31 (sign
> +	# bit of a 32-bit int) set.  None of these are representable
> +	# in 32 bits, and hence all should fail.
> +	check_failure 0x0000010000000000
> +	check_failure 0x0000010080000000
> +	check_failure 0x000001ff7fffffff
> +	check_failure 0x000001ffffffffff
> +	check_failure 0xffffffff7fffffff


> +	check_failure 0xffffffffffffffff

This s64 version of -1

> +	check_failure 0xffffff0000000000
> +	check_failure 0xffffff0080000000
> +}

It was still unclear from the comments and manually looking at the
values why they are clear candidates to always test from all respective
64-bit values. A comment per each would be useful.

  Luis