Bump dependency opencontainers/runc@v1.0.0-rc9

vendor/github.com/opencontainers/runc/libcontainer/utils/utils_unix.go

@@ -3,33 +3,57 @@
 package utils
 
 import (
-	"io/ioutil"
+	"fmt"
 	"os"
 	"strconv"
 
 	"golang.org/x/sys/unix"
 )
 
+// EnsureProcHandle returns whether or not the given file handle is on procfs.
+func EnsureProcHandle(fh *os.File) error {
+	var buf unix.Statfs_t
+	if err := unix.Fstatfs(int(fh.Fd()), &buf); err != nil {
+		return fmt.Errorf("ensure %s is on procfs: %v", fh.Name(), err)
+	}
+	if buf.Type != unix.PROC_SUPER_MAGIC {
+		return fmt.Errorf("%s is not on procfs", fh.Name())
+	}
+	return nil
+}
+
+// CloseExecFrom applies O_CLOEXEC to all file descriptors currently open for
+// the process (except for those below the given fd value).
 func CloseExecFrom(minFd int) error {
-	fdList, err := ioutil.ReadDir("/proc/self/fd")
+	fdDir, err := os.Open("/proc/self/fd")
 	if err != nil {
 		return err
 	}
-	for _, fi := range fdList {
-		fd, err := strconv.Atoi(fi.Name())
+	defer fdDir.Close()
+
+	if err := EnsureProcHandle(fdDir); err != nil {
+		return err
+	}
+
+	fdList, err := fdDir.Readdirnames(-1)
+	if err != nil {
+		return err
+	}
+	for _, fdStr := range fdList {
+		fd, err := strconv.Atoi(fdStr)
+		// Ignore non-numeric file names.
 		if err != nil {
-			// ignore non-numeric file names
 			continue
 		}
-
+		// Ignore descriptors lower than our specified minimum.
 		if fd < minFd {
-			// ignore descriptors lower than our specified minimum
 			continue
 		}
-
-		// intentionally ignore errors from unix.CloseOnExec
+		// Intentionally ignore errors from unix.CloseOnExec -- the cases where
+		// this might fail are basically file descriptors that have already
+		// been closed (including and especially the one that was created when
+		// ioutil.ReadDir did the "opendir" syscall).
 		unix.CloseOnExec(fd)
-		// the cases where this might fail are basically file descriptors that have already been closed (including and especially the one that was created when ioutil.ReadDir did the "opendir" syscall)
 	}
 	return nil
 }