linux-kernel - Re: [PATCH -V6 10/14] hugetlbfs: Add memcg control files for hugetlbfs

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Date:	Mon, 16 Apr 2012 16:13:54 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	linux-mm@...ck.org, mgorman@...e.de,
	kamezawa.hiroyu@...fujitsu.com, dhillf@...il.com,
	aarcange@...hat.com, mhocko@...e.cz, hannes@...xchg.org,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [PATCH -V6 10/14] hugetlbfs: Add memcg control files for
 hugetlbfs

On Mon, 16 Apr 2012 16:14:47 +0530
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> wrote:

> +#ifdef CONFIG_MEM_RES_CTLR_HUGETLB
> +static char *mem_fmt(char *buf, unsigned long n)
> +{
> +	if (n >= (1UL << 30))
> +		sprintf(buf, "%luGB", n >> 30);
> +	else if (n >= (1UL << 20))
> +		sprintf(buf, "%luMB", n >> 20);
> +	else
> +		sprintf(buf, "%luKB", n >> 10);
> +	return buf;
> +}
> +
> +int __init mem_cgroup_hugetlb_file_init(int idx)
> +{
> +	char buf[32];
> +	struct cftype *cft;
> +	struct hstate *h = &hstates[idx];
> +
> +	/* format the size */
> +	mem_fmt(buf, huge_page_size(h));

The sprintf() into a fixed-sized buffer is a bit ugly.  I didn't check
it for possible overflows because 32 looks like "enough".  Actually too
much.

Oh well, it's hard to avoid.  But using scnprintf() would prevent nasty
accidents.

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