container/params: remove confusingly named error

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/init.go

@@ -62,7 +62,7 @@ func Init(prepare func(prefix string), setVerbose func(verbose bool)) {
 		offsetSetup int
 	)
 	if f, err := Receive(setupEnv, &params, &setupFile); err != nil {
-		if errors.Is(err, ErrInvalid) {
+		if errors.Is(err, EBADF) {
 			log.Fatal("invalid setup descriptor")
 		}
 		if errors.Is(err, ErrNotSet) {

container/params.go

@@ -5,11 +5,11 @@ import (
 	"errors"
 	"os"
 	"strconv"
+	"syscall"
 )
 
 var (
-	ErrNotSet  = errors.New("environment variable not set")
-	ErrInvalid = errors.New("bad file descriptor")
+	ErrNotSet = errors.New("environment variable not set")
 )
 
 // Setup appends the read end of a pipe for setup params transmission and returns its fd.
@@ -35,7 +35,7 @@ func Receive(key string, e any, v **os.File) (func() error, error) {
 		} else {
 			setup = os.NewFile(uintptr(fd), "setup")
 			if setup == nil {
-				return nil, ErrInvalid
+				return nil, syscall.EBADF
 			}
 			if v != nil {
 				*v = setup

internal/app/shim_linux.go

@@ -64,7 +64,7 @@ func ShimMain() {
 		closeSetup func() error
 	)
 	if f, err := container.Receive(shimEnv, &params, nil); err != nil {
-		if errors.Is(err, container.ErrInvalid) {
+		if errors.Is(err, syscall.EBADF) {
 			log.Fatal("invalid config descriptor")
 		}
 		if errors.Is(err, container.ErrNotSet) {