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: <20181208184525.GC2952@redhat.com>
Date:   Sat, 8 Dec 2018 13:45:26 -0500
From:   Jerome Glisse <jglisse@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        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>, Jan Kara <jack@...e.cz>,
        tom@...pey.com, Al Viro <viro@...iv.linux.org.uk>, benve@...co.com,
        Christopher Lameter <cl@...ux.com>,
        "Dalessandro, Dennis" <dennis.dalessandro@...el.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        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>
Subject: Re: [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions

On Sat, Dec 08, 2018 at 10:26:04AM -0800, Christoph Hellwig wrote:
> On Sat, Dec 08, 2018 at 12:47:30PM -0500, Jerome Glisse wrote:
> > Most of the user of GUP are well behave (everything under driver/gpu and
> > so is mellanox driver and many other) ie they abide by mmu notifier
> > invalidation call backs. They are a handfull of device driver that thought
> > they could just do GUP and ignore the mmu notifier part and those are the
> > one being problematic. So to me it feels like bystander are be shot for no
> > good reasons.
> 
> get_user_pages is used by every single direct I/O, and while the race
> windows in that case are small they very much exists.

Yes and my proposal allow to fix that in even a better way than
the pin count would ie allowing to provide a callback for write
back to wait on direct I/O as you said for direct I/O it is a
small window so it would be fine to have write back wait on it.

Cheers,
Jérôme