linux-hardening - Re: [PATCH v1 0/6] kunit: build kunit tests without structleak plugin

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Date:   Fri, 17 Sep 2021 09:38:09 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Brendan Higgins <brendanhiggins@...gle.com>
Cc:     Shuah Khan <shuah@...nel.org>, David Gow <davidgow@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Rafael Wysocki <rafael@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Ulf Hansson <ulf.hansson@...aro.org>, andreas.noever@...il.com,
        michael.jamet@...el.com,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        YehezkelShB@...il.com, Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "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>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        gregkh <gregkh@...uxfoundation.org>, linux-iio@...r.kernel.org,
        linux-mmc <linux-mmc@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>,
        linux-hardening@...r.kernel.org,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH v1 0/6] kunit: build kunit tests without structleak plugin

On Fri, Sep 17, 2021 at 8:10 AM Brendan Higgins
<brendanhiggins@...gle.com> wrote:
>
> The structleak plugin causes the stack frame size to grow immensely when
> used with KUnit; this is caused because KUnit allocates lots of
> moderately sized structs on the stack as part of its assertion macro
> implementation. For most tests with small to moderately sized tests
> cases there are never enough KUnit assertions to be an issue at all;
> even when a single test cases has many KUnit assertions, the compiler
> should never put all these struct allocations on the stack at the same
> time since the scope of the structs is so limited; however, the
> structleak plugin does not seem to respect the compiler doing the right
> thing and will still warn of excessive stack size in some cases.
>
> These patches are not a permanent solution since new tests can be added
> with huge test cases, but this serves as a stop gap to stop structleak
> from being used on KUnit tests which will currently result in excessive
> stack size.
>
> Of the following patches, I think the thunderbolt patch may be
> unnecessary since Linus already fixed that test. Additionally, I was not
> able to reproduce the error on the sdhci-of-aspeed test. Nevertheless, I
> included these tests cases for completeness. Please see my discussion
> with Arnd for more context[1].
>
> NOTE: Arnd did the legwork for most of these patches, but did not
> actually share code for some of them, so I left his Signed-off-by off of
> those patches as I don't want to misrepresent him. Arnd, please sign off
> on those patches at your soonest convenience.

Thanks a lot for picking up this work where I dropped the ball.

Patches 1-5 look good to me, and I replied on one remaining issue I see
with patch 6. I think you did more work on these that I did, by doing
a nice write-up and splitting them into separate patches with useful
changelogs, you should keep authorship, and just change my
S-o-b to Suggested-by.

If you prefer to keep me as the author, then the correct way would
be to commit them with --author= to ensure that the author and
first s-o-b match.

        Arnd