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Fri, 7 Aug 2020 15:29:52 +0000 (UTC) Date: Fri, 7 Aug 2020 16:29:49 +0100 From: "Dr. David Alan Gilbert" To: "misono.tomohiro@fujitsu.com" Subject: Re: [PATCH v2 3/3] virtiofsd: probe unshare(CLONE_FS) and print an error Message-ID: <20200807152949.GF2780@work-vm> References: <20200727190223.422280-1-stefanha@redhat.com> <20200727190223.422280-4-stefanha@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=dgilbert@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/07 02:21:37 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: "vromanso@redhat.com" , Daniel Walsh , "qemu-devel@nongnu.org" , "rmohr@redhat.com" , "virtio-fs@redhat.com" , 'Stefan Hajnoczi' , "mpatel@redhat.com" , "vgoyal@redhat.com" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * misono.tomohiro@fujitsu.com (misono.tomohiro@fujitsu.com) wrote: > > Subject: [PATCH v2 3/3] virtiofsd: probe unshare(CLONE_FS) and print an error > > > > An assertion failure is raised during request processing if > > unshare(CLONE_FS) fails. Implement a probe at startup so the problem can > > be detected right away. > > > > Unfortunately Docker/Moby does not include unshare in the seccomp.json > > list unless CAP_SYS_ADMIN is given. Other seccomp.json lists always > > include unshare (e.g. podman is unaffected): > > https://raw.githubusercontent.com/seccomp/containers-golang/master/seccomp.json > > > > Use "docker run --security-opt seccomp=path/to/seccomp.json ..." if the > > default seccomp.json is missing unshare. > > Hi, sorry for a bit late. > > unshare() was added to fix xattr problem: > https://github.com/qemu/qemu/commit/bdfd66788349acc43cd3f1298718ad491663cfcc# > In theory we don't need to call unshare if xattr is disabled, but it is hard to get to know > if xattr is enabled or disabled in fv_queue_worker(), right? > > So, it looks good to me. > Reviewed-by: Misono Tomohiro OK, I think it might also be OK to just fail the xattr operation on a non-file/directory in this case. Dave > Regards, > Misono > > > > > Cc: Misono Tomohiro > > Signed-off-by: Stefan Hajnoczi > > --- > > tools/virtiofsd/fuse_virtio.c | 16 ++++++++++++++++ > > 1 file changed, 16 insertions(+) > > > > diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c > > index 3b6d16a041..9e5537506c 100644 > > --- a/tools/virtiofsd/fuse_virtio.c > > +++ b/tools/virtiofsd/fuse_virtio.c > > @@ -949,6 +949,22 @@ int virtio_session_mount(struct fuse_session *se) > > { > > int ret; > > > > + /* > > + * Test that unshare(CLONE_FS) works. fv_queue_worker() will need it. It's > > + * an unprivileged system call but some Docker/Moby versions are known to > > + * reject it via seccomp when CAP_SYS_ADMIN is not given. > > + * > > + * Note that the program is single-threaded here so this syscall has no > > + * visible effect and is safe to make. > > + */ > > + ret = unshare(CLONE_FS); > > + if (ret == -1 && errno == EPERM) { > > + fuse_log(FUSE_LOG_ERR, "unshare(CLONE_FS) failed with EPERM. If " > > + "running in a container please check that the container " > > + "runtime seccomp policy allows unshare.\n"); > > + return -1; > > + } > > + > > ret = fv_create_listen_socket(se); > > if (ret < 0) { > > return ret; > > -- > > 2.26.2 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK