Does mount /dev/fd inside CageFS has security implications?

Issue

Does mounting /dev/fd inside CageFS, have security implications?

Environment

• CloudLinux
• CageFS
• /dev/fd

Solution

Adding /dev/fd to the default CageFS device list is a generally safe change.

/dev/fd is typically a symlink to /proc/self/fd, which exposes a per-process view of its own open file descriptors.

But if the real /proc/self/fd is not accessible inside the cage, the symlink will break or point to an inaccessible location. So, just ensure that /proc/self/fd is visible and properly mounted inside CageFS as well.