Andrei Vagin <avagin@xxxxxxxxxxxxx> writes: > On Tue, May 09, 2017 at 07:34:00PM -0500, Eric W. Biederman wrote: >> Andrei Vagin <avagin@xxxxxxxxxx> writes: >> >> > The introduced ioctl returns a file descriptor that refers to a owning >> > user namespace for a superblock which is associated with a target file >> > descriptor. >> > >> > EPERM is returned if the current process doesn't have CAP_SYS_ADMIN in >> > the returned user namespace. >> > >> > This information is required to dump and restore mount namespaces. We >> > need to know to which user namespace a superblock is belonged to. >> > >> > We already have the SIOCGSKNS ioctl for sockets to get a network >> > namespace, so it looks reasonable to use the same interface for >> > superblocks too. >> > >> > This functionality can be useful for users in order to understand >> > a running system. >> >> This will probably work. And the capability check eases any concerns >> I might have that this would be a trivial information leak. >> >> That said can we hold off just a little bit. If open_fs work actually >> turns into a real interface that would seem to be the perfect place >> to stick this functionality. > > Sure, we can. Do you know any place where to read more information about > open_fs? I think I have heared a few times about this idea, but it would be > good to get more details. Look for David Howells <dhowells@xxxxxxxxxx> recent patches on lkml he has implemented an initial rfc for it. Eric
