Serge E. Hallyn [serue@xxxxxxxxxx] wrote: | Quoting sukadev@xxxxxxxxxx (sukadev@xxxxxxxxxx): | > Serge E. Hallyn [serue@xxxxxxxxxx] wrote: | > | > | I suppose you could just create /dev/pts/ptmx and /dev/pts/tty. | > | > | Recommend that in containers /dev/ptmx and /dev/tty be symlinks | > | > | into /dev/pts. Applications don't need to change. If | > | > | ptmx_open() sees that inode->i_sb is a devptsfs, it gets the | > | > | namespace from the sb. If not, then it was a device in /dev | > | > | and it gets the nmespace from current. | > | > | > | > But we would still depend on user-space remounting /dev/pts after | > | > the clone right ? Until they do that we would access the parent | > | > container's /dev/pts/ptmx ? | > | | > | Yes. Which is the right thing to do imo. | > | > Hmm, that sounds reasonable, although slightly inconsistent with pid-ns, | > where pid starts at 1 regardless of whether /proc is remounted. | | Very different cases. The pid is the task's pid in the new pidns. | The task ALSO has a different pid in the parent pidns. | | The pts only has an identity in one ptsns. | | > But even so, if user fails to establish the symlink, clones the pts ns | > and tries to create a pty, we would end up with different pts nses again ? | | Yes. So what? We would end up allocating a pts index from child-pts-ns (i.e index 0) and attempt to open /dev/pts/0 which could be an existing pty in the parent pts ns ? | | > i.e | > /dev/ptmx is still a char dev in root fs | > clone(pts_ns) | > ( In child, (before remount /dev/pts)) | > open("/dev/ptmx") | > open("/dev/pts/0") | > | > Since ptmx is not in devpts, we use current_pts_ns() or child-pts-ns | > Since /dev/pts is not remounted in child, we get the parent pts-ns from | > | > If we can somehow detect the incorrect configuration and fail either | > open, we should be ok :-) | | I completely disagree with this sentiment. The kernel doesn't need | to detect an "incorrect configuration" if it isn't dangerous. One | man's "incorrect configuration" is another man's useful trick. Myabe configuration is the wrong word, but unless I am missing something above, spanning two pts-nses is an error condition ? _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers