ebiederm@xxxxxxxxxxxx (Eric W. Biederman) writes: > Andrew Vagin <avagin@xxxxxxxxxxxxx> writes: > >> All these thoughts about security make me thinking that kcmp is what we >> should use here. It's maybe something like this: >> >> kcmp(pid1, pid2, KCMP_NS_USERNS, fd1, fd2) >> >> - to check if userns of the fd1 namepsace is equal to the fd2 userns >> >> kcmp(pid1, pid2, KCMP_NS_PARENT, fd1, fd2) >> >> - to check if a parent namespace of the fd1 pidns is equal to fd pidns. >> >> fd1 and fd2 is file descriptors to namespace files. >> >> So if we want to build a hierarchy, we need to collect all namespaces >> and then enumerate them to check dependencies with help of kcmp. > > That is certainly one way to go. > > There is a funny case where we would want to compare a user namespace > file descriptor to a parent user namespace file descriptor. > > > Grumble, Grumble. I think this may actually a case for creating ioctls > for these two cases. Now that random nsfs file descriptors are bind > mountable the original reason for using proc files is not as pressing. > > One ioctl for the user namespace that owns a file descriptor. > One ioctl for the parent namespace of a namespace file descriptor. > > We also need some way to get a command file descriptor for a file system > super block. Al Viro has a pet project for cleaning up the mount API > and this might be the idea excuse to start looking at that. > > (In principle we might be able to run commands through the namespace > file descriptor and using an ioctl feels dirty. But an ioctl that > only uses the fd and request argument does not suffer from the same > problems that ioctls that have to pass additional arguments suffer > from.) Of course it should be an error perhaps -EINVAL to get a user namespace owner or parent namespace that is outside of a processes current user namespace or pid namespace. That way thing stay bounded within the current namespaces the process is in. Which prevents any leak possibilities, and keeps CRIU working. Eric _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
