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[49.181.38.249]) by smtp.gmail.com with ESMTPSA id k18-20020a170902c41200b001d8f12b0009sm423859plk.293.2024.02.05.15.34.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 Feb 2024 15:34:48 -0800 (PST) Received: from dave by dread.disaster.area with local (Exim 4.96) (envelope-from ) id 1rX8UA-002agH-2H; Tue, 06 Feb 2024 10:34:46 +1100 Date: Tue, 6 Feb 2024 10:34:46 +1100 From: Dave Chinner To: James Gowans Cc: linux-kernel@vger.kernel.org, Eric Biederman , kexec@lists.infradead.org, Joerg Roedel , Will Deacon , iommu@lists.linux.dev, Alexander Viro , Christian Brauner , linux-fsdevel@vger.kernel.org, Paolo Bonzini , Sean Christopherson , kvm@vger.kernel.org, Andrew Morton , linux-mm@kvack.org, Alexander Graf , David Woodhouse , "Jan H . Schoenherr" , Usama Arif , Anthony Yznaga , Stanislav Kinsburskii , madvenka@linux.microsoft.com, steven.sistare@oracle.com, yuleixzhang@tencent.com Subject: Re: [RFC 05/18] pkernfs: add file mmap callback Message-ID: References: <20240205120203.60312-1-jgowans@amazon.com> <20240205120203.60312-6-jgowans@amazon.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240205120203.60312-6-jgowans@amazon.com> On Mon, Feb 05, 2024 at 12:01:50PM +0000, James Gowans wrote: > Make the file data useable to userspace by adding mmap. That's all that > QEMU needs for guest RAM, so that's all be bother implementing for now. > > When mmaping the file the VMA is marked as PFNMAP to indicate that there > are no struct pages for the memory in this VMA. Remap_pfn_range() is > used to actually populate the page tables. All PTEs are pre-faulted into > the pgtables at mmap time so that the pgtables are useable when this > virtual address range is given to VFIO's MAP_DMA. And so what happens when this file is truncated whilst it is mmap()d by an application? Ain't that just a great big UAF waiting to be exploited? -Dave. -- Dave Chinner david@fromorbit.com