On 6/10/2020 12:59 AM, Andrei Vagin wrote: > 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. Y'all keep saying "unprivileged processes" when you mean "processes with less than root privilege". A process with CAP_CHECKPOINT_RESTORE *is* a privileged process. It would have different privilege from a process with CAP_SYS_ADMIN (the current case) but is not "unprivileged". > 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
