linux-kernel - Re: [PATCH v2] hugetlb: clean up potential spectre issue warnings

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Date:   Mon, 21 Feb 2022 09:42:39 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Zhenguo Yao <yaozhenguo1@...il.com>,
        Liu Yuntao <liuyuntao10@...wei.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2] hugetlb: clean up potential spectre issue warnings

On Fri 18-02-22 13:29:46, Mike Kravetz wrote:
[...]
> @@ -4161,7 +4162,7 @@ static int __init hugepages_setup(char *s)
>  			}
>  			if (tmp >= nr_online_nodes)
>  				goto invalid;
> -			node = tmp;
> +			node = array_index_nospec(tmp, nr_online_nodes);
>  			p += count + 1;
>  			/* Parse hugepages */
>  			if (sscanf(p, "%lu%n", &tmp, &count) != 1)
> @@ -6889,9 +6890,9 @@ static int __init cmdline_parse_hugetlb_cma(char *p)
>  			break;
>  
>  		if (s[count] == ':') {
> -			nid = tmp;
> -			if (nid < 0 || nid >= MAX_NUMNODES)
> +			if (tmp >= MAX_NUMNODES)
>  				break;
> +			nid = array_index_nospec(tmp, MAX_NUMNODES);
>  
>  			s += count + 1;
>  			tmp = memparse(s, &s);

This is an early boot code, how is this supposed to be used as a side
channel?
-- 
Michal Hocko
SUSE Labs