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[142.162.112.119]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-89077253218sm159988626d6.43.2026.01.13.08.49.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Jan 2026 08:49:23 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vfha7-00000003vHg-0bmX; Tue, 13 Jan 2026 12:49:23 -0400 Date: Tue, 13 Jan 2026 12:49:23 -0400 From: Jason Gunthorpe To: Zhiping Zhang Cc: Leon Romanovsky , Bjorn Helgaas , linux-rdma@vger.kernel.org, linux-pci@vger.kernel.org, netdev@vger.kernel.org, Keith Busch , Yochai Cohen , Yishai Hadas Subject: Re: [RFC 2/2] Set steering-tag directly for PCIe P2P memory access Message-ID: <20260113164923.GQ745888@ziepe.ca> References: <20260106005758.GM125261@ziepe.ca> <20260113074318.941459-1-zhipingz@meta.com> Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260113074318.941459-1-zhipingz@meta.com> On Mon, Jan 12, 2026 at 11:43:13PM -0800, Zhiping Zhang wrote: > Got it, thanks for pointing out the security concern! To address this, I > propose that we still pass the TPH value when allocating the dmah, but we add > a verification callback in the reg_mr_dmabuf flow to the dmabuf exporter. This > callback will ensure that the TPH value is correctly linked to the exporting > device’s MMIO, and only the exporter can authorize the TPH/tag association. That still sounds messy because we have to protect CPU memory. I think you should not use dmah possibly and make it so the dmabuf entirely supplies the TPH value. Jason