linux-hardening - Re: [PATCH v7 2/5] lib: fix memparse() to handle overflow

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Message-ID: <aY3XTDhPmUQB2V4P@smile.fi.intel.com>
Date: Thu, 12 Feb 2026 15:36:12 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Dmitry Antipov <dmantipov@...dex.ru>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	David Laight <david.laight.linux@...il.com>,
	Kees Cook <kees@...nel.org>, "Darrick J . Wong" <djwong@...nel.org>,
	linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/5] lib: fix memparse() to handle overflow

On Thu, Feb 12, 2026 at 03:56:25PM +0300, Dmitry Antipov wrote:
> Since '_parse_integer_limit()' (and so 'simple_strtoull()') is now
> capable to handle overflow, adjust 'memparse()' to handle overflow
> (denoted by ULLONG_MAX) returned from 'simple_strtoull()'. Also
> use 'check_shl_overflow()' to catch an overflow possibly caused
> by processing size suffix and denote it with ULLONG_MAX as well.

Assuming this is a desired check and you undertake any required
action in case of user breakage, the code wise this version LGTM,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...el.com>

...

> +	if (shl && likely(ptr != endptr)) {

IIUC the second check is not needed, but harmless as it's basically a shortcut
for a single allowed unit letter.

> +		/* Have valid suffix with preceding number. */
> +		unsigned long long val;
> +
> +		if (unlikely(check_shl_overflow(ret, shl, &val)))
> +			ret = ULLONG_MAX;
> +		else

Id est if we came here with ret == 0, shl == 0, we would get val == 0.

> +			ret = val;
> +		endptr++;
> +	}

-- 
With Best Regards,
Andy Shevchenko