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bh=+DTzCWtkAYWXXwDS71eiC1B/ZYAtPEUDUkQAuCNxmV0=; b=FO+0w1AQKuhLRS/B0XsKaxVIJ4TMt6Vb1mgLYT+zNPAEPMRsQt2S9BkCcjqkaGLVlHNehH JPjyMMjjWE+qDtjPqC3rSlspO/EipRkXP7r2y6dVT16agPgHdzq+FXZslqNjIm3iUVlVNy qpga4EJjZK3iDUd1FZ7m2w5MBkNjG40= X-MC-Unique: 5SAXAgUaPwKyb32WpT4kTw-1 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Subject: [PATCH v2 3/3] virtiofsd: probe unshare(CLONE_FS) and print an error Date: Mon, 27 Jul 2020 20:02:23 +0100 Message-Id: <20200727190223.422280-4-stefanha@redhat.com> In-Reply-To: <20200727190223.422280-1-stefanha@redhat.com> References: <20200727190223.422280-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=205.139.110.61; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/27 01:46:13 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 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, MIME_BASE64_TEXT=1.741, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, 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 , "Dr. David Alan Gilbert" , rmohr@redhat.com, virtio-fs@redhat.com, Misono Tomohiro , Stefan Hajnoczi , mpatel@redhat.com, vgoyal@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" 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=3Dpath/to/seccomp.json ..." if the default seccomp.json is missing unshare. Cc: Misono Tomohiro Signed-off-by: Stefan Hajnoczi Reviewed-by: Misono Tomohiro --- 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; =20 + /* + * 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 =3D unshare(CLONE_FS); + if (ret =3D=3D -1 && errno =3D=3D 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 =3D fv_create_listen_socket(se); if (ret < 0) { return ret; --=20 2.26.2