On Tue, Jun 09, 2020 at 06:14:27PM +0200, Christian Brauner wrote: > On Tue, Jun 09, 2020 at 09:06:27AM -0700, Andrei Vagin wrote: > > On Tue, Jun 09, 2020 at 09:44:22AM +0200, Christian Brauner wrote: > > > On Mon, Jun 08, 2020 at 08:42:21PM -0700, Andrei Vagin wrote: ... > > > > 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. > > ... > > I don't suggest to remove or > > downgrade this capability check. The patch allows all c/r related > > operations if the current has CAP_CHECKPOINT_RESTORE. > > > > So in this case the check: > > if (!capable(CAP_SYS_ADMIN)) > > return -EPERM; > > > > will be converted in: > > if (!capable(CAP_SYS_ADMIN) && !capable(CAP_CHECKPOINT_RESTORE)) > > return -EPERM; > > Yeah, I got that but what's the goal here? Isn't it that you want to > make it safe to install the criu binary with the CAP_CHECKPOINT_RESTORE > fscap set so that unprivileged users can restore their own processes > without creating a new user namespace or am I missing something? The > use-cases in the cover-letter make it sound like that's what this is > leading up to: > > > > > * 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. > > But maybe I'm just misunderstanding crucial bits (likely (TM)). I think you understand this right. The goal is to make it possible to use C/R functionality for unprivileged processes. And for me, here are two separate tasks. The first one is how to allow unprivileged users to use C/R from the root user namespace. This is what we discuss here. And another one is how to allow to use C/R functionality from a non-root user namespaces. The second task is about downgrading capable to ns_capable for map_files and PTRACE_O_SUSPEND_SECCOMP. Thanks, Andrei
