linux-kernel - Re: [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Yxig+zfA2Pr4vk6K@nvidia.com>
Date:   Wed, 7 Sep 2022 10:47:39 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Nicolin Chen <nicolinc@...dia.com>, will@...nel.org,
        robin.murphy@....com, alex.williamson@...hat.com,
        suravee.suthikulpanit@....com, marcan@...can.st,
        sven@...npeter.dev, alyssa@...enzweig.io, robdclark@...il.com,
        dwmw2@...radead.org, baolu.lu@...ux.intel.com,
        mjrosato@...ux.ibm.com, gerald.schaefer@...ux.ibm.com,
        orsonzhai@...il.com, baolin.wang@...ux.alibaba.com,
        zhang.lyra@...il.com, thierry.reding@...il.com, vdumpa@...dia.com,
        jonathanh@...dia.com, jean-philippe@...aro.org, cohuck@...hat.com,
        tglx@...utronix.de, shameerali.kolothum.thodi@...wei.com,
        thunder.leizhen@...wei.com, christophe.jaillet@...adoo.fr,
        yangyingliang@...wei.com, jon@...id-run.com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, asahi@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-tegra@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        kevin.tian@...el.com
Subject: Re: [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible
 domain and device/group

On Wed, Sep 07, 2022 at 02:41:54PM +0200, Joerg Roedel wrote:
> On Mon, Aug 15, 2022 at 11:14:33AM -0700, Nicolin Chen wrote:
> > Provide a dedicated errno from the IOMMU driver during attach that the
> > reason attached failed is because of domain incompatability. EMEDIUMTYPE
> > is chosen because it is never used within the iommu subsystem today and
> > evokes a sense that the 'medium' aka the domain is incompatible.
> 
> I am not a fan of re-using EMEDIUMTYPE or any other special value. What
> is needed here in EINVAL, but with a way to tell the caller which of the
> function parameters is actually invalid.

Using errnos to indicate the nature of failure is a well established
unix practice, it is why we have hundreds of error codes and don't
just return -EINVAL for everything.

What don't you like about it?

Would you be happier if we wrote it like

 #define IOMMU_EINCOMPATIBLE_DEVICE xx

Which tells "which of the function parameters is actually invalid" ?

> For that I prefer adding an additional pointer parameter to the attach
> functions in which the reason for the failure can be communicated up the
> chain.

That sounds like OS/2 :\

Jason