On Wed, Dec 5, 2018 at 12:53 PM Christian Brauner <christian@xxxxxxxxxx> wrote: > On Wed, Dec 05, 2018 at 12:20:43PM -0600, Eric W. Biederman wrote: > > Christian Brauner <christian@xxxxxxxxxx> writes: > > > [1]: https://lkml.org/lkml/2018/11/18/130 > > > [2]: https://lore.kernel.org/lkml/874lbtjvtd.fsf@xxxxxxxxxxxxxxxxxxxxxxxxx/ > > > [3]: https://lore.kernel.org/lkml/20181204132604.aspfupwjgjx6fhva@xxxxxxxxxx/ > > > [4]: https://lore.kernel.org/lkml/20181203180224.fkvw4kajtbvru2ku@xxxxxxxxxx/ > > > [5]: https://lore.kernel.org/lkml/20181121213946.GA10795@xxxxxxxxxxxxxxx/ > > > [6]: https://lore.kernel.org/lkml/20181120103111.etlqp7zop34v6nv4@xxxxxxxxxx/ > > > [7]: https://lore.kernel.org/lkml/36323361-90BD-41AF-AB5B-EE0D7BA02C21@xxxxxxxxxxxxxx/ > > > [8]: https://lore.kernel.org/lkml/87tvjxp8pc.fsf@xxxxxxxxxxxx/ > > > [9]: https://asciinema.org/a/X1J8eGhe3vCfBE2b9TXtTaSJ7 > > > [10]: https://lore.kernel.org/lkml/20181203180224.fkvw4kajtbvru2ku@xxxxxxxxxx/ > > > [11]: https://lore.kernel.org/lkml/F53D6D38-3521-4C20-9034-5AF447DF62FF@xxxxxxxxxxxxxx/ I nominate this for 2018's most-well-documented syscall commit log award. ;) > > > + /* > > > + * Give userspace a way to detect whether /proc/<pid>/task/<tid> fds > > > + * are supported. > > > + */ > > > + ret = -EOPNOTSUPP; > > > + if (proc_is_tid_procfd(f.file)) > > > + goto err; > > > > -EBADF is the proper error code. > > This is done so that userspace has a way of figuring out that tid fds > are not yet supported. This has been discussed with Florian (see commit > message). Right, we should keep this -EOPNOTSUPP. > > > + /* Is this a procfd? */ > > > + ret = -EINVAL; > > > + if (!proc_is_tgid_procfd(f.file)) > > > + goto err; > > > > -EBADF is the proper error code. Yeah, EINVAL tends to be used for bad flags... this is more about an improper fd. > > > > > + /* Without CONFIG_PROC_FS proc_pid() returns NULL. */ > > > + pid = proc_pid(file_inode(f.file)); > > > + if (!pid) > > > + goto err; > > > > Perhaps you want to fold the proc_pid into the proc_is_tgid_procfd > > call. That way proc_pid can stay private to proc. > > Hm, I guess we can do that for now. My intention was to have reuseable > helpers but I guess it would be fine for now. > > > > > > + if (!may_signal_procfd(pid)) > > > + goto err; > > > + Does the ns parent checking in may_signal_procfd need any locking or RCU? I know pid and current namespaces are "pinned", but I don't know how parent ns works here. I'm assuming the parents are stuck until all children go away? > > > + ret = kill_pid_info(sig, &kinfo, pid); Just double-checking for myself: this does not bypass security_task_kill(), so no problem there AFAIK. Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> -- Kees Cook
