On Sat, Jun 17, 2006 at 11:36:35AM +0200, Jan Engelhardt wrote: > >> >I assume you're talking about this kind of situation: > >> > > >> >mount --bind /local/writable/dir /chroot/untrusted/area/ > >> >mount --o remount,ro /chroot/untrusted/area/ > >> > >> Well, actually about some kind of VPS: openvz or something like that. > >> But yes, this is the same kind of scenario. > > > >yes, Linux-VServer provides this kind of ro --bind mounts > >without the race, as the the flags are passed on the actual > >mount > > > >> >This has no r/w window in the chroot area: > >> > > >> >mount --bind /local/writable/dir /tmp/area/ > >> >mount --o remount,ro /tmp/area/ > >> >mount --bind /tmp/area/ /chroot/untrusted/area/ > >> >umount /tmp/area/ > >> > >> Well, it looks a little scarry and complicated at first. And probably > >> requires you to know that semantic of --bind lets you do the last > >> unmount. But if you are saying that this makes kernel smaller, faster > >> and less buggy then you are probably very right. > > > >well, it makes the kernel more consistant in it's behaviour, > >because especially for --rbind mounts, the logic what is > >changed where and when is not as well defined as one would > >wish ... > > > >btw, you could get the same result by simply doing: > > > >mount --bind /local/writable/dir /tmp/area/ > >mount --o remount,ro /tmp/area/ > >mount --move /tmp/area/ /chroot/untrusted/area/ > > > > Just a nitpick, you all use "--o" ... :) > mount: option `--o' is ambiguous sorry, copy paste error on my side :) (probably for Dave too ...) best, Herbert > Jan Engelhardt > -- - 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
