@@ -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;
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. Cc: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> --- tools/virtiofsd/fuse_virtio.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)