On Mon, Jun 08, 2020 at 08:42:21PM -0700, Andrei Vagin wrote: > On Wed, Jun 03, 2020 at 06:23:26PM +0200, Adrian Reber wrote: > > This patch introduces CAP_CHECKPOINT_RESTORE, a new capability facilitating > > checkpoint/restore for non-root users. > > > > Over the last years, The CRIU (Checkpoint/Restore In Userspace) team has been > > asked numerous times if it is possible to checkpoint/restore a process as > > non-root. The answer usually was: 'almost'. > > > > The main blocker to restore a process as non-root was to control the PID of the > > restored process. This feature available via the clone3 system call, or via > > /proc/sys/kernel/ns_last_pid is unfortunately guarded by CAP_SYS_ADMIN. > > > > In the past two years, requests for non-root checkpoint/restore have increased > > due to the following use cases: > > * Checkpoint/Restore in an HPC environment in combination with a resource > > manager distributing jobs where users are always running as non-root. > > There is a desire to provide a way to checkpoint and restore long running > > jobs. > > * Container migration as non-root > > * We have been in contact with JVM developers who are integrating > > CRIU into a Java VM to decrease the startup time. These checkpoint/restore > > applications are not meant to be running with CAP_SYS_ADMIN. > > > ... > > > > The introduced capability allows to: > > * Control PIDs when the current user is CAP_CHECKPOINT_RESTORE capable > > for the corresponding PID namespace via ns_last_pid/clone3. > > * Open files in /proc/pid/map_files when the current user is > > CAP_CHECKPOINT_RESTORE capable in the root namespace, useful for recovering > > files that are unreachable via the file system such as deleted files, or memfd > > files. > > PTRACE_O_SUSPEND_SECCOMP is needed for C/R and it is protected by > CAP_SYS_ADMIN too. This is currently capable(CAP_SYS_ADMIN) (init_ns capable) why is it safe to allow unprivileged users to suspend security policies? That sounds like a bad idea. if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) { if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) || !IS_ENABLED(CONFIG_SECCOMP)) return -EINVAL; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (seccomp_mode(¤t->seccomp) != SECCOMP_MODE_DISABLED || current->ptrace & PT_SUSPEND_SECCOMP) return -EPERM; } Christian