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To: Max Reitz , Miklos Szeredi References: <599fd4bd-2f62-1ce5-2b9c-0512ee7ead6e@redhat.com> <0208dde6-df57-c27a-418f-57cb3c0173f2@redhat.com> From: Laszlo Ersek Message-ID: Date: Mon, 21 Dec 2020 13:45:09 +0100 MIME-Version: 1.0 In-Reply-To: <0208dde6-df57-c27a-418f-57cb3c0173f2@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=lersek@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=lersek@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "=?UTF-8?Q?Daniel_P._Berrang=c3=a9?=" , qemu devel list , "Dr. David Alan Gilbert" , virtio-fs@redhat.com, Stefan Hajnoczi , Vivek Goyal Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/21/20 13:06, Max Reitz wrote: > I can share sshfs through sshfs, so it must be something virtiofs-specific. Your insight proved crucial to solving the riddle. Chaining sshfs with sshfs made me think that you must have used a normal (non-root) user account on the first remote computer (where you ran the 2nd sshfs command). And that reminded me of the "allow_root" option which I seemed to have read somewhere around the FUSE manuals. So indeed I set up another sshfs mount on my laptop, with my normal UID, and tried to access the mount point from a plain root shell (with virtiofsd completely out of the picture) -- it failed with "Permission denied". :) It's apparently intentional on sshfs's / FUSE's part, to protect the local root user from "remote nastiness injection". Then I re-did the sshfs mount, but with "-o allow_root" this time. The plain root shell can now access the mount point. ... So can virtiofsd :) It's *amazing* to see remote files in the UEFI shell. I never thought "filesystem as a service" could feel this empowering. Thanks, Max! Laszlo