On Tue, Dec 04, 2018 at 11:05:46AM -0500, Stephen Smalley wrote: > On 12/4/18 10:42 AM, Vivek Goyal wrote: > > On Tue, Dec 04, 2018 at 04:31:09PM +0100, Miklos Szeredi wrote: > > > On Tue, Dec 4, 2018 at 4:22 PM Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > > > > > > > Having said that, this still create little anomaly when mknod to client > > > > is not allowed on context label. So a device file, which is on lower > > > > and client can not open it for read/write on host, it can now be opened > > > > for read/write because mounter will allow access. So why it is different > > > > that regular copy up. Well, in regular copy up, we created a copy of > > > > the original object and allowed writing to that object (cp --preserve=all) > > > > model. But in case of device file, writes will go to same original > > > > object. (And not a separate copy). > > > > > > That's true. > > > > > > In that sense copy up of special file should result in upper having > > > the same label as of lower, right? > > > > I guess that might be reasonable (if this behavior is a concern). So even > > after copy up, client will not be able to read/write a device if it was > > not allowed on lower. > > > > Stephen, what do you think about retaining label of lower for device > > files during copy up. What about socket/fifo. > > We don't check client task access to the upper inode label, only to the > overlay, right? So the client is still free to access the device through > the overlay even if we preserve the lower inode label on the upper inode? > What do we gain? That's only with latest code and Miklos said he will revert it for 4.20. IOW, I am assuming that we will continue to check access to a file on upper in the context of mounter. Otherwise, client will be able to access files on upper/ which even mounter can't access. Thanks Vivek
