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package container
import (
"bytes"
"log"
"os"
"strconv"
"sync"
)
var (
kernelOverflowuid int
kernelOverflowgid int
kernelCapLastCap int
sysctlOnce sync.Once
)
const (
kernelOverflowuidPath = "/proc/sys/kernel/overflowuid"
kernelOverflowgidPath = "/proc/sys/kernel/overflowgid"
kernelCapLastCapPath = "/proc/sys/kernel/cap_last_cap"
)
func mustReadSysctl() {
if v, err := os.ReadFile(kernelOverflowuidPath); err != nil {
log.Fatalf("cannot read %q: %v", kernelOverflowuidPath, err)
} else if kernelOverflowuid, err = strconv.Atoi(string(bytes.TrimSpace(v))); err != nil {
log.Fatalf("cannot interpret %q: %v", kernelOverflowuidPath, err)
}
if v, err := os.ReadFile(kernelOverflowgidPath); err != nil {
log.Fatalf("cannot read %q: %v", kernelOverflowgidPath, err)
} else if kernelOverflowgid, err = strconv.Atoi(string(bytes.TrimSpace(v))); err != nil {
log.Fatalf("cannot interpret %q: %v", kernelOverflowgidPath, err)
}
if v, err := os.ReadFile(kernelCapLastCapPath); err != nil {
log.Fatalf("cannot read %q: %v", kernelCapLastCapPath, err)
} else if kernelCapLastCap, err = strconv.Atoi(string(bytes.TrimSpace(v))); err != nil {
log.Fatalf("cannot interpret %q: %v", kernelCapLastCapPath, err)
}
}
func OverflowUid() int { sysctlOnce.Do(mustReadSysctl); return kernelOverflowuid }
func OverflowGid() int { sysctlOnce.Do(mustReadSysctl); return kernelOverflowgid }
func LastCap() uintptr { sysctlOnce.Do(mustReadSysctl); return uintptr(kernelCapLastCap) }
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