linux-kernel - Re: [PATCH 3/5] iommu/s390: Use RCU to allow concurrent domain

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: <68d91d7a5aadbd46dc34470eccd6b86a84c9e47b.camel@linux.ibm.com>
Date:   Fri, 21 Oct 2022 14:08:02 +0200
From:   Niklas Schnelle <schnelle@...ux.ibm.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Matthew Rosato <mjrosato@...ux.ibm.com>, iommu@...ts.linux.dev,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Gerd Bayer <gbayer@...ux.ibm.com>,
        Pierre Morel <pmorel@...ux.ibm.com>,
        linux-s390@...r.kernel.org, borntraeger@...ux.ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
        svens@...ux.ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] iommu/s390: Use RCU to allow concurrent domain_list
 iteration

On Thu, 2022-10-20 at 08:05 -0300, Jason Gunthorpe wrote:
> On Thu, Oct 20, 2022 at 10:51:10AM +0200, Niklas Schnelle wrote:
> 
> > Ok that makes sense thanks for the explanation. So yes my assessment is
> > still that in this situation the IOTLB flush is architected to return
> > an error that we can ignore. Not the most elegant I admit but at least
> > it's simple. Alternatively I guess we could use call_rcu() to do the
> > zpci_unregister_ioat() but I'm not sure how to then make sure that a
> > subsequent zpci_register_ioat() only happens after that without adding
> > too much more logic.
> 
> This won't work either as the domain could have been freed before the
> call_rcu() happens, the domain needs to be detached synchronously
> 
> Jason

Yeah right, that is basically the same issue I was thinking of for a
subsequent zpci_register_ioat(). What about the obvious one. Just call
synchronize_rcu() before zpci_unregister_ioat()?