bug: kernel version comparison in setup.sh is lexicographic, not numeric

[jpleva91]

Bug: String comparison for kernel version

File: scripts/setup.sh

The OpenShell prerequisite check compares the Linux kernel version as a string:

if [[ "$(uname -r | cut -d. -f1-2)" < "5.13" ]]; then
    warn "Kernel $(uname -r) — Landlock needs >= 5.13"
fi

Bash's [[ < ]] operator performs lexicographic (alphabetical) comparison, not numeric comparison. This means:

Kernel	cut output	String comparison result	Correct?
5.4	5.4	"5.4" < "5.13" → false (4 > 1)	❌ should warn, doesn't
5.9	5.9	"5.9" < "5.13" → false (9 > 1)	❌ should warn, doesn't
5.13	5.13	"5.13" < "5.13" → false	✓
6.0	6.0	"6.0" < "5.13" → false	✓

Kernels 5.4–5.12 (which don't support Landlock) will not trigger the warning, potentially leading to a broken OpenShell install.

Fix

kernel_maj=$(uname -r | cut -d. -f1)
kernel_min=$(uname -r | cut -d. -f2)
if (( kernel_maj < 5 || (kernel_maj == 5 && kernel_min < 13) )); then
    warn "Kernel $(uname -r) — Landlock needs >= 5.13"
fi