When a docker container is confined with AppArmor [1] and happens to run
on top of a kernel that supports mount mediation [2], e.g. any Ubuntu
kernel, mount(2) returns EACCES instead of EPERM. This then leads to:
elogind-logind[33]: Failed to mount per-user tmpfs directory /run/user/1000: Permission denied
login[42]: pam_elogind(login:session): Failed to create session: Access denied
and user sessions don't start.
This also applies to selinux that too returns EACCES on mount denial.
[1] https://github.com/docker/docker/blob/master/docs/security/apparmor.md#understand-the-policies
[2] http://bazaar.launchpad.net/~apparmor-dev/apparmor/master/view/head:/kernel-patches/4.7/0025-UBUNTU-SAUCE-apparmor-Add-the-ability-to-mediate-mou.patch
r = mount("tmpfs", u->runtime_path, "tmpfs", MS_NODEV|MS_NOSUID, t);
if (r < 0) {
r = mount("tmpfs", u->runtime_path, "tmpfs", MS_NODEV|MS_NOSUID, t);
if (r < 0) {
+ if (errno != EPERM && errno != EACCES) {
r = log_error_errno(errno, "Failed to mount per-user tmpfs directory %s: %m", u->runtime_path);
goto fail;
}
r = log_error_errno(errno, "Failed to mount per-user tmpfs directory %s: %m", u->runtime_path);
goto fail;
}
- /* Lacking permissions, maybe
- * CAP_SYS_ADMIN-less container? In this case,
- * just use a normal directory. */
+ log_debug_errno(errno, "Failed to mount per-user tmpfs directory %s, assuming containerized execution, ignoring: %m", u->runtime_path);
r = chmod_and_chown(u->runtime_path, 0700, u->uid, u->gid);
if (r < 0) {
r = chmod_and_chown(u->runtime_path, 0700, u->uid, u->gid);
if (r < 0) {