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Mon, 21 Jun 2021 10:18:17 -0700 (PDT) X-Google-Smtp-Source: ABdhPJz/sUuD6XPLG3Pl6wRJdJzMuOibTbDtqa7qI3X+oV8L6H6tma0CRBIN+EQ5j+sGN2zqtN39aw== X-Received: by 2002:a17:907:9c9:: with SMTP id bx9mr24190261ejc.144.1624295897756; Mon, 21 Jun 2021 10:18:17 -0700 (PDT) Received: from dresden.str.redhat.com ([2a02:908:1e46:160:b272:8083:d5:bc7d]) by smtp.gmail.com with ESMTPSA id x9sm5212586ejc.37.2021.06.21.10.18.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Jun 2021 10:18:17 -0700 (PDT) Subject: Re: [PATCH 0/4] export/fuse: Allow other users access to the export To: Kevin Wolf References: <20210614144407.134243-1-mreitz@redhat.com> From: Max Reitz Message-ID: <9af03389-8c6d-6610-9326-61c65e8eac30@redhat.com> Date: Mon, 21 Jun 2021 19:18:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=170.10.133.124; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.373, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=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: qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 21.06.21 18:12, Kevin Wolf wrote: > Am 14.06.2021 um 16:44 hat Max Reitz geschrieben: >> Hi, >> >> With the default mount options, FUSE mounts are not accessible to any >> users but the one who did the mount, not even to root. To allow such >> accesses, allow_other must be passed. >> >> This is probably useful to some people (it certainly is to me, e.g. when >> exporting some image as my normal user, and then trying to loop mount it >> as root), so this series adds a QAPI allow-other bool that will make the >> FUSE export code pass allow_other,default_permissions to FUSE. >> >> (default_permissions will make the kernel do the usual UNIX permission >> checks, which is something that makes a lot of sense when allowing other >> users access to the export.) >> >> This also requires our SETATTR code to be able to handle permission >> changes, though, so the user can then run chmod/chown/chgrp on the >> export to adjust its permissions to their need. >> >> The final patch adds a test. > If there is even a use case for leaving the option off (not trusting > root?), it must certainly be the less common case? So I'm not sure if > allow-other should be an option at all, but if it is, enabling it by > default would make more sense to me. > > Is there a reason why you picked false as the default, except that it is > the old behaviour? No. :) Well, mostly.  I also thought, if FUSE thinks allow_other shouldn’t be the default, who am I to decide otherwise. Now that I tried to find out why FUSE has it as the default (I only remember vague “security reasons”), I still couldn’t find out why, but I did find that using this option as non-root user requires /etc/fuse.conf to have user_allow_other in it, which I don’t think we can require. So I think it must be an option.  As for which value should be the default, that probably depends on how common having user_allow_other in /etc/fuse.conf is.  I know I never put it there, and it’s both on my Fedora and my Arch system.  So I guess it seems rather common? Max