Hello! I use Arch Linux and a tool called udevil to mount external devices.
My problem is that /run/media permissions prevent me from mounting pendrives:
1. No pendrive, no /run/media directory.
2. I put the pendrive, a 700 root:root /run/media is created.
3. Chmod it to 755 to let me mount.
My questions are:
1. What decides permissions on this directory?
2. How can I avoid chmoding? A systemd tmpfile should do the job, but I did not try and it would be not elegant.

No fstab entries, mtab entry is:
run /run tmpfs rw,nosuid,nodev,relatime,mode=755 0 0

EDIT: Ok, umask issue.