linux-kernel - Re: [PATCH 1/2] mm: introduce put_user

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: <CAPcyv4irkynLsEz=HRwLZacnRX6ifNRFX7ibAN_R+9yqR143bQ@mail.gmail.com>
Date:   Wed, 12 Dec 2018 15:54:26 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Jérôme Glisse <jglisse@...hat.com>,
        Jan Kara <jack@...e.cz>, John Hubbard <jhubbard@...dia.com>,
        Matthew Wilcox <willy@...radead.org>,
        John Hubbard <john.hubbard@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>, tom@...pey.com,
        Al Viro <viro@...iv.linux.org.uk>, benve@...co.com,
        Christoph Hellwig <hch@...radead.org>,
        Christopher Lameter <cl@...ux.com>,
        "Dalessandro, Dennis" <dennis.dalessandro@...el.com>,
        Doug Ledford <dledford@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Mike Marciniszyn <mike.marciniszyn@...el.com>,
        rcampbell@...dia.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        "Weiny, Ira" <ira.weiny@...el.com>
Subject: Re: [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions

On Wed, Dec 12, 2018 at 3:37 PM Jason Gunthorpe <jgg@...pe.ca> wrote:
>
> On Wed, Dec 12, 2018 at 04:53:49PM -0500, Jerome Glisse wrote:
> > > Almost, we need some safety around assuming that DMA is complete the
> > > page, so the notification would need to go all to way to userspace
> > > with something like a file lease notification. It would also need to
> > > be backstopped by an IOMMU in the case where the hardware does not /
> > > can not stop in-flight DMA.
> >
> > You can always reprogram the hardware right away it will redirect
> > any dma to the crappy page.
>
> That causes silent data corruption for RDMA users - we can't do that.
>
> The only way out for current hardware is to forcibly terminate the
> RDMA activity somehow (and I'm not even sure this is possible, at
> least it would be driver specific)
>
> Even the IOMMU idea probably doesn't work, I doubt all current
> hardware can handle a PCI-E error TLP properly.

My thinking here is that we would at least have the infrastructure for
userspace to opt-in to getting the callback, the threat of an IOMMU
forcibly tearing down mappings, and likely some identification for
pages that are revocable. With "long term" pins I would hope to move
any detection of incompatibility to the memory registration phase
rather than something unacceptable like injecting random truncate
failures.