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

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Message-ID: <CAFd5g46Z_vVb92Y-sfWi68=HFy5+kukZXvT9usEEnhBUvPg3AQ@mail.gmail.com>
Date:   Tue, 3 Dec 2019 15:44:18 -0800
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     David Gow <davidgow@...gle.com>, Kees Cook <keescook@...omium.org>
Cc:     shuah <shuah@...nel.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>
Subject: Re: [PATCH kselftest/test] kunit: Always print actual pointer values
 in asserts

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).

>
> Signed-off-by: David Gow <davidgow@...gle.com>

Reviewed-by: Brendan Higgins <brendanhiggins@...gle.com>

Thanks!