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Date: Tue, 19 May 2026 12:37:40 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Thorsten Blum <thorsten.blum@linux.dev>
Cc: Kees Cook <kees@kernel.org>, Andy Shevchenko <andy@kernel.org>,
 linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] string: use min in sized_strscpy
Message-Id: <20260519123740.458d905f958f39d41cb130fd@linux-foundation.org>
In-Reply-To: <20260514165601.527883-3-thorsten.blum@linux.dev>
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On Thu, 14 May 2026 18:56:03 +0200 Thorsten Blum <thorsten.blum@linux.dev> wrote:

> Use min() and drop the limit variable to simplify sized_strscpy().

Why is this code so messy.   Never seen so many typecasts per inch.

> @@ -125,11 +126,8 @@ ssize_t sized_strscpy(char *dest, const char *src, size_t count)
>  	 * If src is unaligned, don't cross a page boundary,
>  	 * since we don't know if the next page is mapped.
>  	 */
> -	if ((long)src & (sizeof(long) - 1)) {
> -		size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
> -		if (limit < max)
> -			max = limit;
> -	}
> +	if ((long)src & (sizeof(long) - 1))

That looks like IS_ALIGNED()?

> +		max = min(PAGE_SIZE - ((long)src & (PAGE_SIZE - 1)), max);

That looks like a dog's breakfast.

And a bit like ALIGN_DOWN.  Not quite, but I'm sure we have helpers for
whatever this is doing.

>  #else
>  	/* If src or dest is unaligned, don't do word-at-a-time. */
>  	if (((long) dest | (long) src) & (sizeof(long) - 1))

gargh.


Oh well, not your fault.  I'll grab the patch, thanks.