Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220209134018.8242-1-liuyuntao10@huawei.com> <95d1dc4e-fc3b-fe3c-5d85-218a7410e966@oracle.com>
In-Reply-To: <95d1dc4e-fc3b-fe3c-5d85-218a7410e966@oracle.com>
From:   Zhenguo Yao <yaozhenguo1@gmail.com>
Date:   Mon, 28 Feb 2022 10:59:07 +0800
Message-ID: <CA+WzARn63QzU0h2NfPDzgk=fs5=uiHHGaXZcye+qmGyLWRoFog@mail.gmail.com>
Subject: Re: [PATCH] hugetlbfs: fix a truncation issue in hugepages parameter
To:     Mike Kravetz <mike.kravetz@oracle.com>
Cc:     liuyuntao <liuyuntao10@huawei.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        linux-kernel@vger.kernel.org, wuxu.wu@huawei.com,
        fangchuangchuang@huawei.com, windspectator@gmail.com
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Mike Kravetz <mike.kravetz@oracle.com> =E4=BA=8E2022=E5=B9=B42=E6=9C=8810=
=E6=97=A5=E5=91=A8=E5=9B=9B 08:44=E5=86=99=E9=81=93=EF=BC=9A
>
> On 2/9/22 05:40, liuyuntao wrote:
> > From: Liu Yuntao <liuyuntao10@huawei.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 =3D tmp;
> >
> > For example, add following parameter in command line:
> >       hugepagesz=3D1G hugepages=3D4294967297:5
> > 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 p=
arameter to support node allocation")
> > Signed-off-by: Liu Yuntao <liuyuntao10@huawei.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 supp=
ort node specific alloc, ignoring!\n");
> >                               return 0;
> >                       }
> > +                     if (tmp >=3D nr_online_nodes)
> > +                             goto invalid;
> >                       node =3D tmp;
>
> I am surprised none of the automated checking complained about that
> assignment.
>
> >                       p +=3D count + 1;
> > -                     if (node < 0 || node >=3D 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?
>
Sorry for my late reply.  This check for node < 0 was added
to handle node parameter overflow from the earliest version:
https://lore.kernel.org/lkml/20210820030536.25737-1-yaozhenguo1@gmail.com/
Parameter of node allocation was:  hugepages_node=3Dxx hugepages=3Dxx at th=
is
version. With the changing of the code, this check has lost its effect.

> > -                             goto invalid;
> >                       /* Parse hugepages */
> >                       if (sscanf(p, "%lu%n", &tmp, &count) !=3D 1)
> >                               goto invalid;
>
> Thanks,
>
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
>
> --
> Mike Kravetz