linux-kernel - Re: [PATCH] kcsan: test: don't put the expect array on the stack

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Date:   Wed, 28 Dec 2022 22:12:01 +0100
From:   Marco Elver <elver@...gle.com>
To:     Max Filippov <jcmvbkbc@...il.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, linux-xtensa@...ux-xtensa.org
Subject: Re: [PATCH] kcsan: test: don't put the expect array on the stack

On Fri, 23 Dec 2022 at 08:42, Max Filippov <jcmvbkbc@...il.com> wrote:
>
> Size of the 'expect' array in the __report_matches is 1536 bytes, which
> is exactly the default frame size warning limit of the xtensa
> architecture.
> As a result allmodconfig xtensa kernel builds with the gcc that does not
> support the compiler plugins (which otherwise would push the said
> warning limit to 2K) fail with the following message:
>
>   kernel/kcsan/kcsan_test.c:257:1: error: the frame size of 1680 bytes
>     is larger than 1536 bytes
>
> Fix it by dynamically alocating the 'expect' array.
>
> Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
> ---
>  kernel/kcsan/kcsan_test.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
> index dcec1b743c69..af62ec51bd5f 100644
> --- a/kernel/kcsan/kcsan_test.c
> +++ b/kernel/kcsan/kcsan_test.c
> @@ -159,7 +159,7 @@ static bool __report_matches(const struct expect_report *r)
>         const bool is_assert = (r->access[0].type | r->access[1].type) & KCSAN_ACCESS_ASSERT;
>         bool ret = false;
>         unsigned long flags;
> -       typeof(observed.lines) expect;
> +       typeof(*observed.lines) *expect;
>         const char *end;
>         char *cur;
>         int i;
> @@ -168,6 +168,10 @@ static bool __report_matches(const struct expect_report *r)
>         if (!report_available())
>                 return false;
>
> +       expect = kmalloc(sizeof(observed.lines), GFP_KERNEL);
> +       if (!expect)

WARN_ON(), because this may either spuriously fail or pass a test
case, and we'd want to know about that.

Thanks,
-- Marco