On Fri, Mar 13, 2009 at 10:27:54AM -0700, Linus Torvalds wrote: > On Thu, 12 Mar 2009, Sukadev Bhattiprolu wrote: > > > Ying Han [yinghan@xxxxxxxxxx] wrote: > > | Hi Serge: > > | I made a patch based on Oren's tree recently which implement a new > > | syscall clone_with_pid. I tested with checkpoint/restart process tree > > | and it works as expected. > > > > Yes, I think we had a version of clone() with pid a while ago. > > Are people _at_all_ thinking about security? > > Obviously not. For the record, OpenVZ always have CAP_SYS_ADMIN check on restore. And CAP_SYS_ADMIN will be in version to be sent out. Not having it is one big security hole. > There's no way we can do anything like this. Sure, it's trivial to do > inside the kernel. But it also sounds like a _wonderful_ attack vector > against badly written user-land software that sends signals and has small > races. > > Quite frankly, from having followed the discussion(s) over the last few > weeks about checkpoint/restart in various forms, my reaction to just about > _all_ of this is that people pushing this are pretty damn borderline. > > I think you guys are working on all the wrong problems. > > Let's face it, we're not going to _ever_ checkpoint any kind of general > case process. Just TCP makes that fundamentally impossible in the general > case, and there are lots and lots of other cases too (just something as > totally _trivial_ as all the files in the filesystem that don't get rolled > back). What do you mean here? Unlinked files? > So unless people start realizing that > (a) processes that want to be checkpointed had better be ready and aware > of it, and help out This is not going to happen. Userspace authors won't do anything (nor they shouldn't). > (b) there's no way in hell that we're going to add these kinds of > interfaces that have dubious upsides (just teach the damn program > you're checkpointing that pids will change, and admit to everybody > that people who want to be checkpointed need to do work) and are > potential security holes. I personally don't understand why on earth clone_with_pid() is again with us. As if pids are somehow unique among other resources. It was discussed when IPC objects creation with specific parameters were discussed. "struct pid" and "struct pid_namespace" can be trivially restored without leaking to userspace. People probably assume that task should be restored with clone(2) which is unnatural given relations between task_struct, nsproxy and individual struct foo_namespace's > (c) if you are going to play any deeper games, you need to have > privileges. IOW, "clone_with_pid()" is ok for _root_, but not for > some random user. And you'd better keep that in mind EVERY SINGLE > STEP OF THE WAY. > > I'm really fed up with these discussions. I have seen almost _zero_ > critical thinking at all. Probably because anybody who is in the least > doubtful about it simply has tuned out the discussion. So here's my input: > start small, start over, and start thinking about other issues than just > checkpointing. _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
