linux-hardening - Re: [PATCH v2 06/14] lib/string_kunit: add correctness test for strnlen

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Message-ID: <aWYFT1yoktjDLFTm@smile.fi.intel.com>
Date: Tue, 13 Jan 2026 10:41:51 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Feng Jiang <jiangfeng@...inos.cn>
Cc: pjw@...nel.org, palmer@...belt.com, aou@...s.berkeley.edu,
	alex@...ti.fr, kees@...nel.org, andy@...nel.org,
	akpm@...ux-foundation.org, ebiggers@...nel.org,
	martin.petersen@...cle.com, ardb@...nel.org,
	ajones@...tanamicro.com, conor.dooley@...rochip.com,
	samuel.holland@...ive.com, linus.walleij@...aro.org,
	nathan@...nel.org, linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 06/14] lib/string_kunit: add correctness test for
 strnlen

On Tue, Jan 13, 2026 at 04:27:40PM +0800, Feng Jiang wrote:
> Add a KUnit test for strnlen() to verify correctness across
> different string lengths and memory alignments.

...

> +	for (offset = 0; offset < STRING_TEST_MAX_OFFSET; offset++) {
> +		for (len = 0; len <= STRING_TEST_MAX_LEN; len++) {
> +			s[offset + len] = '\0';

This should be one or two characters further so you check should also check for
non-NUL terminated strings...

> +			if (len > 0)
> +				KUNIT_EXPECT_EQ(test, strnlen(s + offset, len - 1), len - 1);

...or make more tests, with len - 2 at least.

> +			KUNIT_EXPECT_EQ(test, strnlen(s + offset, len), len);

> +			KUNIT_EXPECT_EQ(test, strnlen(s + offset, len + 1), len);

I would also add + 2 test case.

> +			KUNIT_EXPECT_EQ(test, strnlen(s + offset, len + 10), len);

> +			s[offset + len] = 'A';
> +		}
> +	}
> +}

-- 
With Best Regards,
Andy Shevchenko