linux-kernel - Re: [PATCH kselftest/test] kunit: Always print actual pointer values in asserts

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Message-ID: <2246e35f-b8c4-0152-91f5-5f01d52cd414@kernel.org>
Date:   Wed, 25 Mar 2020 11:25:59 -0600
From:   shuah <shuah@...nel.org>
To:     Brendan Higgins <brendanhiggins@...gle.com>,
        David Gow <davidgow@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        KUnit Development <kunit-dev@...glegroups.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        shuah <shuah@...nel.org>
Subject: Re: [PATCH kselftest/test] kunit: Always print actual pointer values
 in asserts

On 3/25/20 10:33 AM, Brendan Higgins wrote:
> On Tue, Mar 24, 2020 at 8:33 PM David Gow <davidgow@...gle.com> wrote:
>>
>> On Tue, Dec 3, 2019 at 3:44 PM Brendan Higgins
>> <brendanhiggins@...gle.com> wrote:
>>>
>>> On Thu, Nov 21, 2019 at 3:51 PM David Gow <davidgow@...gle.com> wrote:
>>>>
>>>> KUnit assertions and expectations will print the values being tested. If
>>>> these are pointers (e.g., KUNIT_EXPECT_PTR_EQ(test, a, b)), these
>>>> pointers are currently printed with the %pK format specifier, which -- to
>>>> prevent information leaks which may compromise, e.g., ASLR -- are often
>>>> either hashed or replaced with ____ptrval____ or similar, making debugging
>>>> tests difficult.
>>>>
>>>> By replacing %pK with %px as Documentation/core-api/printk-formats.rst
>>>> suggests, we disable this security feature for KUnit assertions and
>>>> expectations, allowing the actual pointer values to be printed. Given
>>>> that KUnit is not intended for use in production kernels, and the
>>>> pointers are only printed on failing tests, this seems like a worthwhile
>>>> tradeoff.
>>>
>>> I agree. However, I also remember that others in the past yelled at me
>>> for assuming that KUnit would not be built into production kernels.
>>>
>>> I feel like +Kees Cook would have a good opinion on this (or will at
>>> least CC the right people).
>>>
>>
>> I'm tempted to take the silence as a sign that no-one is upset by
>> this. Otherwise, consider this a gentle reminder to file any
>> objections you may have. :-)
>>
>> Otherwise, I've confirmed that this still applies cleanly to the
>> latest linux-kselftest/kunit branch, so -- assuming there are no
>> last-minute objections -- this ought to be ready to go.
> 
> Shuah, can you pick this up for 5.7?
> 

Yes. I will pick this up.

thanks,
-- Shuah