linux-kernel - Re: [PATCH v3 1/3] selftests/mm/write_to_hugetlbfs: parse -s as size

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Message-ID: <20251223121104.6614c1e3@pumpkin>
Date: Tue, 23 Dec 2025 12:11:04 +0000
From: David Laight <david.laight.linux@...il.com>
To: Li Wang <liwang@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, David Hildenbrand <david@...nel.org>, Mark Brown
 <broonie@...nel.org>, Shuah Khan <shuah@...nel.org>, Waiman Long
 <longman@...hat.com>
Subject: Re: [PATCH v3 1/3] selftests/mm/write_to_hugetlbfs: parse -s as
 size_t

On Tue, 23 Dec 2025 17:29:38 +0800
Li Wang <liwang@...hat.com> wrote:

> David Laight <david.laight.linux@...il.com> wrote:
> 

> > What was wrong with atoi() ?  
> 
> As the patch summary described, write_to_hugetlbfs previously parsed -s via
> atoi() into an int, which can overflow and print negative sizes. This
> problem was
> found on our kernel-64k platform and
> 
>  #./charge_reserved_hugetlb.sh -cgroup-v2
>  # -----------------------------------------
>  ...
>  # nr hugepages = 10
>  # writing cgroup limit: 5368709120
>  # writing reseravation limit: 5368709120
>  ...
>  # Writing to this path: /mnt/huge/test
>  # Writing this size: -1610612736        <--------

So the problem was that atoi() doesn't let you specify valid values
over 2GB.
That isn't how I read the patch summary.
It read as though you were worried about detecting invalid input.

	David