vendor: github.com/moby/sys/userns v0.2.1

userns: fix user-namespace detection on OpenVZ, where namespace inode
numbers are virtualized.

full diff: https://github.com/moby/sys/userns/compare/v0.2.0...v0.2.1

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor/github.com/moby/sys/userns/userns_linux.go

@@ -2,6 +2,7 @@ package userns
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"os"
 	"sync"
@@ -23,7 +24,16 @@ var inUserNS = sync.OnceValue(runningInUserNS)
 func runningInUserNS() bool {
 	var st syscall.Stat_t
 	if err := syscall.Stat("/proc/self/ns/user", &st); err == nil {
-		return st.Ino != procUserInitIno
+		// The kernel's initial user namespace inode is definitive when it
+		// matches. OpenVZ virtualizes namespace inode numbers, so a mismatch
+		// must fall back to uid_map-based detection there.
+		if st.Ino == procUserInitIno {
+			return false
+		}
+		if runningInOpenVZ() {
+			return runningInUserNSFromUIDMap()
+		}
+		return true
 	} else if !os.IsNotExist(err) {
 		// As long as /proc/self/ns/user exists, we are on a modern kernel.
 		// Other errors indicate an unexpected procfs state, where assuming the
@@ -35,6 +45,10 @@ func runningInUserNS() bool {
 	// through procfs at /proc/self/ns/user.
 	// TODO: Remove this fallback once Linux kernels older than 3.8 are no
 	// longer supported.
+	return runningInUserNSFromUIDMap()
+}
+
+func runningInUserNSFromUIDMap() bool {
 	file, err := os.Open("/proc/self/uid_map")
 	if err != nil {
 		// This kernel-provided file only exists if user namespaces are supported.
@@ -69,3 +83,19 @@ func uidMapInUserNS(uidMap string) bool {
 	initNS := a == 0 && b == 0 && c == 4294967295
 	return !initNS
 }
+
+// runningInOpenVZ reports whether the process is running inside an OpenVZ
+// container.
+//
+// OpenVZ exposes /proc/vz both on the host and inside containers, while
+// /proc/bc is only exposed on the host. This follows systemd's OpenVZ
+// detection:
+// https://github.com/systemd/systemd/blob/v261.2/src/basic/virt.c#L642-L653
+func runningInOpenVZ() bool {
+	var st syscall.Stat_t
+	if err := syscall.Stat("/proc/vz", &st); err != nil {
+		return false
+	}
+	err := syscall.Stat("/proc/bc", &st)
+	return errors.Is(err, syscall.ENOENT)
+}

vendor/modules.txt

@@ -231,7 +231,7 @@ github.com/moby/sys/symlink
 # github.com/moby/sys/user v0.4.1
 ## explicit; go 1.18
 github.com/moby/sys/user
-# github.com/moby/sys/userns v0.2.0
+# github.com/moby/sys/userns v0.2.1
 ## explicit; go 1.21
 github.com/moby/sys/userns
 # github.com/moby/term v0.5.2