linux-hardening - Re: [PATCH v4 1/3] lib: introduce simple error-checking wrapper for memparse()

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Message-ID: <aW-VDu4aPV6kZv80@smile.fi.intel.com>
Date: Tue, 20 Jan 2026 16:45:34 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Dmitry Antipov <dmantipov@...dex.ru>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <kees@...nel.org>,
	Carlos Maiolino <cem@...nel.org>,
	Christoph Hellwig <hch@...radead.org>, linux-xfs@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v4 1/3] lib: introduce simple error-checking wrapper for
 memparse()

On Tue, Jan 20, 2026 at 05:12:27PM +0300, Dmitry Antipov wrote:
> Introduce 'memvalue()' which uses 'memparse()' to parse a string
> with optional memory suffix into a non-negative number. If parsing
> has succeeded, returns 0 and stores the result at the location
> specified by the second argument. Otherwise returns -EINVAL and
> leaves the location untouched.

...

> +/**
> + *	memvalue -  Wrap memparse() with simple error detection
> + *	@ptr: Where parse begins
> + *	@valptr: Where to store result
> + *
> + *	Uses memparse() to parse a string into a number stored at
> + *	@valptr, leaving memory at @valptr untouched in case of error.
> + *
> + *	Return: -EINVAL for a presumably negative value or if an
> + *	unrecognized character was encountered, and 0 otherwise.
> + */
> +int __must_check memvalue(const char *ptr, unsigned long long *valptr)
> +{
> +	unsigned long long ret;
> +	char *end;
> +
> +	if (*ptr == '-')
> +		return -EINVAL;
> +	ret = memparse(ptr, &end);
> +	if (*end)
> +		return -EINVAL;
> +	*valptr = ret;
> +	return 0;
> +}

My questions seem left unsettled:
- why -EINVAL in the first place and not -ERANGE in the first place;
- why do we need this patch _at all_ based on the how callers are
doing now (w.o. this change), i.o.w. why the memparse() can't be
used directly.


-- 
With Best Regards,
Andy Shevchenko