linux-kernel - Re: [PATCH] kunit: Protect KUNIT_BINARY_STR_ASSERTION against ERR

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Message-ID: <CABVgOSkn1EW6kCocBb6GUyk4h0qQHkDUYmLMs7F9Ja8ii_gOVQ@mail.gmail.com>
Date: Sat, 20 Dec 2025 14:59:15 +0800
From: David Gow <davidgow@...gle.com>
To: Richard Fitzgerald <rf@...nsource.cirrus.com>
Cc: brendan.higgins@...ux.dev, raemoar63@...il.com, 
	linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com, 
	linux-kernel@...r.kernel.org, patches@...nsource.cirrus.com
Subject: Re: [PATCH] kunit: Protect KUNIT_BINARY_STR_ASSERTION against ERR_PTR values

On Sat, 20 Dec 2025 at 00:12, Richard Fitzgerald
<rf@...nsource.cirrus.com> wrote:
>
> Replace the NULL checks with IS_ERR_OR_NULL() in
> KUNIT_BINARY_STR_ASSERTION() to prevent the strcmp() faulting if a
> passed pointer is an ERR_PTR.
>
> Commit 7ece381aa72d4 ("kunit: Protect string comparisons against NULL")
> added the checks for NULL on both pointers so that asserts would fail,
> instead of faulting, if either pointer is NULL. But either pointer
> could hold an ERR_PTR value.
>
> This assumes that the assertion is expecting both strings to be valid,
> and is asserting the equality of their _content_.
>
> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> ---

This looks good to me, though I do acknowledge the general hate for
IS_ERR_OR_NULL()[1], and particularly how it can annoy things like
smatch. For an assertion, though, where we're really asserting that
both are valid strings which are equal, I think this is okay.

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

Cheers,
-- David

[1]: https://staticthinking.wordpress.com/2022/08/01/mixing-error-pointers-and-null/
>  include/kunit/test.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/kunit/test.h b/include/kunit/test.h
> index 5ec5182b5e57..9cd1594ab697 100644
> --- a/include/kunit/test.h
> +++ b/include/kunit/test.h
> @@ -906,7 +906,8 @@ do {                                                                               \
>         };                                                                     \
>                                                                                \
>         _KUNIT_SAVE_LOC(test);                                                 \
> -       if (likely((__left) && (__right) && (strcmp(__left, __right) op 0)))   \
> +       if (likely(!IS_ERR_OR_NULL(__left) && !IS_ERR_OR_NULL(__right) &&      \
> +           (strcmp(__left, __right) op 0)))                                   \
>                 break;                                                         \
>                                                                                \
>                                                                                \
> --
> 2.47.3
>

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