Messages in this thread | | | Date | Mon, 21 Jul 2014 15:09:14 +0200 | Subject | Re: [PATCH 3/3] fuse: Allow mounts from user namespaces | From | Miklos Szeredi <> |
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On Mon, Jul 21, 2014 at 2:47 PM, Seth Forshee <seth.forshee@canonical.com> wrote: > On Fri, Jul 18, 2014 at 05:33:23PM +0200, Miklos Szeredi wrote: >> On Mon, Jul 14, 2014 at 9:18 PM, Seth Forshee >> <seth.forshee@canonical.com> wrote: >> > Update fuse to allow mounts from user namespaces. During mount >> > current_user_ns() is stashed away, >> >> Same thing here. While practically this may work, it's theoretically >> wrong, and possibly may go wrong in special situations. In fuse >> there's no official "server process", so storing information, like >> namespace, about one is going to be wrong. > > What you're suggesting would probably work fine when dealing with pids. > It's not going to work though for the checks I've added in > fuse_allow_current_process() that the process is in the mount owner's > user ns, and without those checks or something similar I don't think > it's safe to permit allow_other for user ns mounts.
You can add that check in fuse_dev_do_read() as well. If the fsuid/fsgid doesn't exist in the "server's" namespace, then set req->out.h.error and call request_end().
> Can you elaborate on what special situations might violate these > assumptions or otherwise cause problems?
What's preventing a fuse fs implementation from handling FUSE_INIT in one process and then handling the rest in a different process (possibly in a different namespace)?
Thanks, Miklos
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