int/linux: add/use Dup3, Open, Openat

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

Author: kolyshkin

internal/linux/linux.go

@@ -6,6 +6,14 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+// Dup3 wraps [unix.Dup3].
+func Dup3(oldfd, newfd, flags int) error {
+	err := retryOnEINTR(func() error {
+		return unix.Dup3(oldfd, newfd, flags)
+	})
+	return os.NewSyscallError("dup3", err)
+}
+
 // Exec wraps [unix.Exec].
 func Exec(cmd string, args []string, env []string) error {
 	err := retryOnEINTR(func() error {
@@ -23,6 +31,28 @@ func Getwd() (wd string, err error) {
 	return wd, os.NewSyscallError("getwd", err)
 }
 
+// Open wraps [unix.Open].
+func Open(path string, mode int, perm uint32) (fd int, err error) {
+	fd, err = retryOnEINTR2(func() (int, error) {
+		return unix.Open(path, mode, perm)
+	})
+	if err != nil {
+		return -1, &os.PathError{Op: "open", Path: path, Err: err}
+	}
+	return fd, nil
+}
+
+// Openat wraps [unix.Openat].
+func Openat(dirfd int, path string, mode int, perm uint32) (fd int, err error) {
+	fd, err = retryOnEINTR2(func() (int, error) {
+		return unix.Openat(dirfd, path, mode, perm)
+	})
+	if err != nil {
+		return -1, &os.PathError{Op: "openat", Path: path, Err: err}
+	}
+	return fd, nil
+}
+
 // Sendmsg wraps [unix.Sendmsg].
 func Sendmsg(fd int, p, oob []byte, to unix.Sockaddr, flags int) error {
 	err := retryOnEINTR(func() error {

libcontainer/console_linux.go

@@ -3,6 +3,7 @@ package libcontainer
 import (
 	"os"
 
+	"github.com/opencontainers/runc/internal/linux"
 	"golang.org/x/sys/unix"
 )
 
@@ -26,16 +27,12 @@ func mountConsole(slavePath string) error {
 // dupStdio opens the slavePath for the console and dups the fds to the current
 // processes stdio, fd 0,1,2.
 func dupStdio(slavePath string) error {
-	fd, err := unix.Open(slavePath, unix.O_RDWR, 0)
+	fd, err := linux.Open(slavePath, unix.O_RDWR, 0)
 	if err != nil {
-		return &os.PathError{
-			Op:   "open",
-			Path: slavePath,
-			Err:  err,
-		}
+		return err
 	}
 	for _, i := range []int{0, 1, 2} {
-		if err := unix.Dup3(fd, i, 0); err != nil {
+		if err := linux.Dup3(fd, i, 0); err != nil {
 			return err
 		}
 	}

libcontainer/rootfs_linux.go

@@ -24,6 +24,7 @@ import (
 	"github.com/opencontainers/cgroups"
 	devices "github.com/opencontainers/cgroups/devices/config"
 	"github.com/opencontainers/cgroups/fs2"
+	"github.com/opencontainers/runc/internal/linux"
 	"github.com/opencontainers/runc/libcontainer/configs"
 	"github.com/opencontainers/runc/libcontainer/utils"
 )
@@ -883,12 +884,8 @@ func reOpenDevNull() error {
 		}
 		if stat.Rdev == devNullStat.Rdev {
 			// Close and re-open the fd.
-			if err := unix.Dup3(int(file.Fd()), fd, 0); err != nil {
-				return &os.PathError{
-					Op:   "dup3",
-					Path: "fd " + strconv.Itoa(int(file.Fd())),
-					Err:  err,
-				}
+			if err := linux.Dup3(int(file.Fd()), fd, 0); err != nil {
+				return err
 			}
 		}
 	}
@@ -1063,15 +1060,15 @@ func pivotRoot(rootfs string) error {
 	// with pivot_root this allows us to pivot without creating directories in
 	// the rootfs. Shout-outs to the LXC developers for giving us this idea.
 
-	oldroot, err := unix.Open("/", unix.O_DIRECTORY|unix.O_RDONLY, 0)
+	oldroot, err := linux.Open("/", unix.O_DIRECTORY|unix.O_RDONLY, 0)
 	if err != nil {
-		return &os.PathError{Op: "open", Path: "/", Err: err}
+		return err
 	}
 	defer unix.Close(oldroot)
 
-	newroot, err := unix.Open(rootfs, unix.O_DIRECTORY|unix.O_RDONLY, 0)
+	newroot, err := linux.Open(rootfs, unix.O_DIRECTORY|unix.O_RDONLY, 0)
 	if err != nil {
-		return &os.PathError{Op: "open", Path: rootfs, Err: err}
+		return err
 	}
 	defer unix.Close(newroot)
 

libcontainer/standard_init_linux.go

@@ -262,9 +262,9 @@ func (l *linuxStandardInit) Init() error {
 	// user process. We open it through /proc/self/fd/$fd, because the fd that
 	// was given to us was an O_PATH fd to the fifo itself. Linux allows us to
 	// re-open an O_PATH fd through /proc.
-	fd, err := unix.Open(fifoPath, unix.O_WRONLY|unix.O_CLOEXEC, 0)
+	fd, err := linux.Open(fifoPath, unix.O_WRONLY|unix.O_CLOEXEC, 0)
 	if err != nil {
-		return &os.PathError{Op: "open exec fifo", Path: fifoPath, Err: err}
+		return err
 	}
 	if _, err := unix.Write(fd, []byte("0")); err != nil {
 		return &os.PathError{Op: "write exec fifo", Path: fifoPath, Err: err}

libcontainer/utils/utils_unix.go

@@ -14,6 +14,7 @@ import (
 	_ "unsafe" // for go:linkname
 
 	securejoin "github.com/cyphar/filepath-securejoin"
+	"github.com/opencontainers/runc/internal/linux"
 	"github.com/sirupsen/logrus"
 	"golang.org/x/sys/unix"
 )
@@ -358,9 +359,9 @@ func Openat(dir *os.File, path string, flags int, mode uint32) (*os.File, error)
 	}
 	flags |= unix.O_CLOEXEC
 
-	fd, err := unix.Openat(dirFd, path, flags, mode)
+	fd, err := linux.Openat(dirFd, path, flags, mode)
 	if err != nil {
-		return nil, &os.PathError{Op: "openat", Path: path, Err: err}
+		return nil, err
 	}
 	return os.NewFile(uintptr(fd), dir.Name()+"/"+path), nil
 }

tests/cmd/seccompagent/seccompagent.go

@@ -14,6 +14,7 @@ import (
 	"strings"
 
 	securejoin "github.com/cyphar/filepath-securejoin"
+	"github.com/opencontainers/runc/internal/linux"
 	"github.com/opencontainers/runtime-spec/specs-go"
 	libseccomp "github.com/seccomp/libseccomp-golang"
 	"github.com/sirupsen/logrus"
@@ -124,7 +125,7 @@ func handleNewMessage(sockfd int) (uintptr, string, error) {
 func readArgString(pid uint32, offset int64) (string, error) {
 	buffer := make([]byte, 4096) // PATH_MAX
 
-	memfd, err := unix.Open(fmt.Sprintf("/proc/%d/mem", pid), unix.O_RDONLY, 0o777)
+	memfd, err := linux.Open(fmt.Sprintf("/proc/%d/mem", pid), unix.O_RDONLY, 0o777)
 	if err != nil {
 		return "", err
 	}