On Tue, Nov 11, 2014 at 04:27:37PM +0100, Miklos Szeredi wrote: > On Wed, Oct 22, 2014 at 04:24:19PM -0500, Seth Forshee wrote: > > Unprivileged users are normally restricted from mounting with the > > allow_other option by system policy, but this could be bypassed > > for a mount done with user namespace root permissions. In such > > cases allow_oth er should not allow users outside the userns > > to access the mount as doing so would give the unprivileged user > > the ability to manipulate processes it would otherwise be unable > > to manipulate. Therefore access with allow_other should be > > restricted to users in the userns as the superblock or a > > descendant of that namespace. > > Fine. > > But aren't this kind of thing supposed to be prevented anyway by having private > mount namespace coupled with the pid-user-whatever namespace? > > It seems like being a bit too careful (not to say that that's a bad thing). A userns mount should be in a "private" mount namespace; specifically the user performing the mount must have CAP_SYS_ADMIN in mnt_ns->user_ns. The mount may still be accessible via /proc/pid/root though, and doing this ensures that in any case the user can never use the mount to manipulate processes that it can't already manipulate. Thanks, Seth -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
