linux-kernel - Re: [PATCH] mm/mmap: Tighten up cmdline_parse_stack_guard

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Message-ID: <ZO3pz+3fAihhrtMU@casper.infradead.org>
Date:   Tue, 29 Aug 2023 13:51:27 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/mmap: Tighten up cmdline_parse_stack_guard_gap()

On Mon, Aug 28, 2023 at 10:52:12AM +0530, Anshuman Khandual wrote:
> -static int __init cmdline_parse_stack_guard_gap(char *p)
> +static int __init cmdline_parse_stack_guard_gap(char *str)
>  {
>  	unsigned long val;
> -	char *endptr;
>  
> -	val = simple_strtoul(p, &endptr, 10);
> -	if (!*endptr)
> -		stack_guard_gap = val << PAGE_SHIFT;
> +	if (!str)
> +		return 0;

Please explain how this function can be called with a NULL pointer.

> -	return 1;
> +	val = simple_strtoul(str, &str, 10);
> +	if (!*str && val) {
> +		stack_guard_gap = val << PAGE_SHIFT;
> +		return 1;
> +	}
> +	return 0;
>  }

Now you've removed the abillity for someone to say stack_guard_gap=0,
which seems potentially useful.