mirror of
https://github.com/opencontainers/runc.git
synced 2026-07-11 06:03:57 +08:00
Sebastiaan van Stijn
d8e9ed3e08
This makes libcontainer/userns self-dependent, largely returning to the original implementation from lxc. The `uiMapInUserNS` is kept as a separate function for unit-testing and fuzzing. Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
56 lines
1.2 KiB
Go
56 lines
1.2 KiB
Go
package userns
|
|
|
|
import (
|
|
"bufio"
|
|
"fmt"
|
|
"os"
|
|
"sync"
|
|
)
|
|
|
|
var (
|
|
inUserNS bool
|
|
nsOnce sync.Once
|
|
)
|
|
|
|
// runningInUserNS detects whether we are currently running in a user namespace.
|
|
//
|
|
// Originally copied from https://github.com/lxc/incus/blob/e45085dd42f826b3c8c3228e9733c0b6f998eafe/shared/util.go#L678-L700.
|
|
func runningInUserNS() bool {
|
|
nsOnce.Do(func() {
|
|
file, err := os.Open("/proc/self/uid_map")
|
|
if err != nil {
|
|
// This kernel-provided file only exists if user namespaces are supported.
|
|
return
|
|
}
|
|
defer file.Close()
|
|
|
|
buf := bufio.NewReader(file)
|
|
l, _, err := buf.ReadLine()
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
inUserNS = uidMapInUserNS(string(l))
|
|
})
|
|
return inUserNS
|
|
}
|
|
|
|
func uidMapInUserNS(uidMap string) bool {
|
|
if uidMap == "" {
|
|
// File exist but empty (the initial state when userns is created,
|
|
// see user_namespaces(7)).
|
|
return true
|
|
}
|
|
|
|
var a, b, c int64
|
|
if _, err := fmt.Sscanf(uidMap, "%d %d %d", &a, &b, &c); err != nil {
|
|
// Assume we are in a regular, non user namespace.
|
|
return false
|
|
}
|
|
|
|
// As per user_namespaces(7), /proc/self/uid_map of
|
|
// the initial user namespace shows 0 0 4294967295.
|
|
initNS := a == 0 && b == 0 && c == 4294967295
|
|
return !initNS
|
|
}
|