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[156.34.48.30]) by smtp.gmail.com with ESMTPSA id o2sm2032427qkk.42.2020.10.07.11.47.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Oct 2020 11:47:06 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kQESv-001Elc-Ob; Wed, 07 Oct 2020 15:47:05 -0300 Date: Wed, 7 Oct 2020 15:47:05 -0300 From: Jason Gunthorpe To: Daniel Vetter Cc: DRI Development , LKML , kvm@vger.kernel.org, Linux MM , Linux ARM , linux-samsung-soc , "open list:DMA BUFFER SHARING FRAMEWORK" , linux-s390@vger.kernel.org, Daniel Vetter , Kees Cook , Dan Williams , Andrew Morton , John Hubbard , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Jan Kara , Alex Williamson , Cornelia Huck Subject: Re: [PATCH 13/13] vfio/type1: Mark follow_pfn as unsafe Message-ID: <20201007184705.GY5177@ziepe.ca> References: <20201007164426.1812530-1-daniel.vetter@ffwll.ch> <20201007164426.1812530-14-daniel.vetter@ffwll.ch> <20201007173911.GX5177@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Bogosity: Ham, tests=bogofilter, spamicity=0.000040, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Oct 07, 2020 at 08:14:06PM +0200, Daniel Vetter wrote: > Hm, but wouldn't need that the semi-nasty vma_open trick to make sure > that vma doesn't untimely disappear? Or is the idea to look up the > underlying vfio object, and refcount that directly? Ah, the patches Alex was working on had the refcount I think, it does need co-ordination across multiple VFIO instances IIRC. At least a simple check would guarentee we only have exposed PCI BAR pages which is not as bad security wise as the other stuff. Jason