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[216.228.121.143]) by mx.google.com with ESMTPS id g15si504873otj.168.2019.06.06.20.37.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 06 Jun 2019 20:37:44 -0700 (PDT) Received-SPF: pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.143 as permitted sender) client-ip=216.228.121.143; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=N8RlWv2x; spf=pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.143 as permitted sender) smtp.mailfrom=jhubbard@nvidia.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate14.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 06 Jun 2019 20:37:41 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 06 Jun 2019 20:37:43 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 06 Jun 2019 20:37:43 -0700 Received: from [10.110.48.28] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 7 Jun 2019 03:37:43 +0000 Subject: Re: [PATCH v2 hmm 09/11] mm/hmm: Poison hmm_range during unregister To: Jason Gunthorpe , Jerome Glisse , "Ralph Campbell" , CC: , , Andrea Arcangeli , , , Jason Gunthorpe References: <20190606184438.31646-1-jgg@ziepe.ca> <20190606184438.31646-10-jgg@ziepe.ca> X-Nvconfidentiality: public From: John Hubbard Message-ID: Date: Thu, 6 Jun 2019 20:37:42 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190606184438.31646-10-jgg@ziepe.ca> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL104.nvidia.com (172.18.146.11) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: quoted-printable DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1559878661; bh=hnXE0MxsnGUyN9sEUkzf3xpow50f6NZj1i458LDKMRY=; h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=N8RlWv2xDfEYSaLNfEgPO8HsRXdEbSEQyaFJIissVJcwJeh7EjuWKFbHWPoKUPURH Oyg92crCE7PWV1skDH1Wku3scQRSMDd14bfAWi5o86TBFjDfjyWCzOrPaqDnbTl4zn XqRZYR7aWKsZMbWTAsMzcVZLDJEioManv8HzxlJokeKWhxh4uXeJ8hD2cstTzfUALU Gc6Xqz2sKONzjUtI1v4WwoaBYZqbiZZHCU1iDWDMoIw3CAJmVktcqr85nR0n6+VTZb MTpSPfxRwhRMQQkkeqmrf4zQs27WL6ZQjPKzghI1xvJN5/Jzgu5WHMLVh2S52fWdU+ FRSERUmJs5aWA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 6/6/19 11:44 AM, Jason Gunthorpe wrote: > From: Jason Gunthorpe >=20 > Trying to misuse a range outside its lifetime is a kernel bug. Use WARN_O= N > and poison bytes to detect this condition. >=20 > Signed-off-by: Jason Gunthorpe > Reviewed-by: J=C3=A9r=C3=B4me Glisse > --- > v2 > - Keep range start/end valid after unregistration (Jerome) > --- > mm/hmm.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) >=20 > diff --git a/mm/hmm.c b/mm/hmm.c > index 6802de7080d172..c2fecb3ecb11e1 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -937,7 +937,7 @@ void hmm_range_unregister(struct hmm_range *range) > struct hmm *hmm =3D range->hmm; > =20 > /* Sanity check this really should not happen. */ That comment can also be deleted, as it has the same meaning as the WARN_ON() that you just added. > - if (hmm =3D=3D NULL || range->end <=3D range->start) > + if (WARN_ON(range->end <=3D range->start)) > return; > =20 > mutex_lock(&hmm->lock); > @@ -948,7 +948,10 @@ void hmm_range_unregister(struct hmm_range *range) > range->valid =3D false; > mmput(hmm->mm); > hmm_put(hmm); > - range->hmm =3D NULL; > + > + /* The range is now invalid, leave it poisoned. */ To be precise, we are poisoning the range's back pointer to it's owning hmm instance. Maybe this is clearer: /* * The range is now invalid, so poison it's hmm pointer.=20 * Leave other range-> fields in place, for the caller's use. */ ...or something like that? > + range->valid =3D false; > + memset(&range->hmm, POISON_INUSE, sizeof(range->hmm)); > } > EXPORT_SYMBOL(hmm_range_unregister); > =20 >=20 The above are very minor documentation points, so: Reviewed-by: John Hubbard thanks, --=20 John Hubbard NVIDIA