linux-kernel - Re: [PATCH] hugetlbfs: fix a truncation issue in hugepages parameter

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Date:   Wed, 9 Feb 2022 16:43:29 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     liuyuntao <liuyuntao10@...wei.com>, akpm@...ux-foundation.org,
        yaozhenguo1@...il.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        wuxu.wu@...wei.com, fangchuangchuang@...wei.com,
        windspectator@...il.com
Subject: Re: [PATCH] hugetlbfs: fix a truncation issue in hugepages parameter

On 2/9/22 05:40, liuyuntao wrote:
> From: Liu Yuntao <liuyuntao10@...wei.com>
> 
> When we specify a large number for node in hugepages parameter,
> it may be parsed to another number due to truncation in this statement:
> 	node = tmp;
> 
> For example, add following parameter in command line:
> 	hugepagesz=1G hugepages=4294967297:5
> and kernel will allocate 5 hugepages for node 1 instead of ignoring it.
> 
> I move the validation check earlier to fix this issue, and slightly
> simplifies the condition here.
> 
> Fixes: b5389086ad7be0 ("hugetlbfs: extend the definition of hugepages parameter to support node allocation")
> Signed-off-by: Liu Yuntao <liuyuntao10@...wei.com>
> ---
>  mm/hugetlb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 61895cc01d09..0929547f6ad6 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4159,10 +4159,10 @@ static int __init hugepages_setup(char *s)
>  				pr_warn("HugeTLB: architecture can't support node specific alloc, ignoring!\n");
>  				return 0;
>  			}
> +			if (tmp >= nr_online_nodes)
> +				goto invalid;
>  			node = tmp;

I am surprised none of the automated checking complained about that
assignment.

>  			p += count + 1;
> -			if (node < 0 || node >= nr_online_nodes)

I can't remember, but I think that check for node < 0 was added to handle
overflow during the above assignment.  Do you remember Zhenguo Yao?
   
> -				goto invalid;
>  			/* Parse hugepages */
>  			if (sscanf(p, "%lu%n", &tmp, &count) != 1)
>  				goto invalid;

Thanks,

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>

-- 
Mike Kravetz