Julien Cristau on 2015/10/22 +0200 @07:47:28: > > That would surely be a regression. Debian went > > from a working X that dropped privileges, to a > > non-working X that can only be run as root. Huh?? > > No, Debian is going from an X server that always runs > as root to one that can run as unprivileged user in > most cases. There was previously no dropping > privileges.
Ok, my mistake; I inferred from being able to "pkill X" successfully as ordinary user, that it was not running as root. It turns out that while X runs with ruid=user (which allows kill(2) to work), it retains euid=0 still the whole time. Thank you for your correction. However, since I'm running KMS, I don't understand why root is needed (ignoring the tty permission issue -- I could make easily make a group for this) in the first place? I found three places which make me think this is both possible and was working at some point: 1. I found a trivial patch[1] that was in both Ubuntu and ChromeOS before, which added a '-nohwaccess' flag to Xorg, which basically just no-oped xf86EnableIOPorts, and it seemed to work fine for people before... 2. I also found a mailing list post[2] indicating that Gentoo Hardened removed ioperm(2) and iopl(2) from their kernel entirely and X still ran fine (with KMS) once it was told to continue (ignore the error). 3. it looks like Xorg itself merged a fix[3][4] to ignore hardware I/O port error, based on comments[5] by keithp. Why can't '-nohwaccess' flag be added to the X server (I'll handle device node permissions myself)? Alternatively, why not just have X drop privs via setreuid() after it does whatever it thinks it has to with the hardware? Also, how does systemd-logind do this? It must have euid=0 itself do the iopl, unless there is some magic trick? Please do not force me to install systemd. I realize I can run the X server as root, but there seems to be a trivial way to make it so that those of us who don't use systemd (but still use Debian) don't have to run our X server as root either. [1] https://lists.debian.org/debian-x/2010/02/msg00371.html [2] http://www.gossamer-threads.com/lists/gentoo/hardened/267371 [3] http://lists.x.org/archives/xorg-devel/2012-June/031980.html [4] http://lists.x.org/archives/xorg-devel/2012-June/031981.html [5] http://lists.x.org/archives/xorg-devel/2012-September/033656.html
