On Mon, Apr 18, 2016 at 11:37:34AM -0400, James Bottomley wrote: > OK, so if you want me to reply properly, you're going to have to keep > my address in the cc list. > > > > If you enter it first, you lose privilege for subsequent > > namespace > > > enters,see issue > > > > > > https://github.com/karelzak/util-linux/issues/315 > > > > > > The fix is to enter the user namespace last of all. > > > > I verified that with *current*/unpatched nsenter, > > > > $ unshare -rm sleep inf & > > $ nsenter -t $! -U -m --preserve > > > > works as expected (from regular user [and with unprivileged userns > > enabled]). > > > > With this patch it *won't* work [verified], of course (as you'll need > > root privileges in userns before joining mount-ns, and you can only > > obtain them by entering userns first). > > So we're using userns for different things. I'm using it to remove > privilege (so on my userns implementation root in the host enters but > on becoming root in the userns, it can do nothing other than write to > its own files) and you're using it to enhance privilege. It looks like > these two things will always be mutually exclusive, so perhaps we need > an extra flag to nsenter to say do the userns first or last? That's what I have talked about at github -- see Eric's comment in the code, the user NS is the first in the array for a good reason. May be it would be really better to add --user-{first,last} options to specify when you want to enter user NS. Karel -- Karel Zak <kzak@xxxxxxxxxx> http://karelzak.blogspot.com -- To unsubscribe from this list: send the line "unsubscribe util-linux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
