On Tue, Dec 6, 2016 at 3:31 PM, Stephen Smalley <[email protected]> wrote: > On 12/06/2016 03:04 PM, Daniel J Walsh wrote: >> Currently in SELinux and UserNamespace can not be enabled with Docker/runc >> at the same time. >> >> Runc mounts tmpfs directories with >> --context="system_u:object_r:container_file_t:s0:c1,c2" type labels >> but the following patch blocks the use of context mounts when using user >> namespace. >> >> http://kernel.suse.com/cgit/kernel/commit/?id=aad82892af261b9903cc11c55be3ecf5f0b0b4f8 >> >> User Namespace has to be established before tmpfs are mounted so we are >> unable to mount a >> tmpfs with a context=flag and UserNamespace enabled. >> >> Controlling the ability to change the label of a mounted file systemd should >> be a MAC decision not a DAC, >> or UserNamespace. Setting the SELinux labels on an object like a file system >> mount point >> should be controlled by SELinux. SELinux should check if the label of the >> process doing the >> mount is able to relabel from the label of the mount point, and labelto the >> specified label. >> >> SELinux does this for privileged processes (running with SYS_ADMIN) so use >> namespace should not be >> any different. Also the process doing the mount would be allowed by DAC to >> set the label of the tmpfs after >> it is mounted (As long as SELinux allowed). >> >> There is no security difference between: >> >> mount -o tmpfs context="foobar" none /dev >> >> >> And >> >> mount -o tmpfs none /dev >> >> chcon foobar -R /dev >> >> >> The second would not be blocked by usernamespace. >> >> Bottom line this patch should be reverted so container runtimes like docker >> can use both User Namespace >> and SELinux at the same time. > > I doubt we want to revert it entirely. Looks like Smack has an explicit > exemption for tmpfs/ramfs (and sysfs, but it wouldn't really make sense > to do it there). We could do something similar.
Yes, I still think the restriction makes sense for persistent filesystems, but for things like tmpfs it does seem silly. -- paul moore www.paul-moore.com _______________________________________________ Selinux mailing list [email protected] To unsubscribe, send email to [email protected]. To get help, send an email containing "help" to [email protected].
