Update to runc main, removing pin to an older version

We were pinned to a specific commit to ensure that tests kept
passing. Hopefully they pass now, as we need to grab latest runc
for CVE fixes.

Also grab Buildah main to fix a build issue on FreeBSD. After a
botched manual vendor, I used Ed's treadmill script and squashed
it into this commit to make Git happy. Thanks bunches Ed.

Signed-off-by: Matt Heon <mheon@redhat.com>

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

@@ -5,10 +5,9 @@ package utils
 
 import (
 	"fmt"
-	"math"
 	"os"
 	"strconv"
-	"sync"
+	_ "unsafe" // for go:linkname
 
 	"golang.org/x/sys/unix"
 )
@@ -25,38 +24,11 @@ func EnsureProcHandle(fh *os.File) error {
 	return nil
 }
 
-var (
-	haveCloseRangeCloexecBool bool
-	haveCloseRangeCloexecOnce sync.Once
-)
-
-func haveCloseRangeCloexec() bool {
-	haveCloseRangeCloexecOnce.Do(func() {
-		// Make sure we're not closing a random file descriptor.
-		tmpFd, err := unix.FcntlInt(0, unix.F_DUPFD_CLOEXEC, 0)
-		if err != nil {
-			return
-		}
-		defer unix.Close(tmpFd)
-
-		err = unix.CloseRange(uint(tmpFd), uint(tmpFd), unix.CLOSE_RANGE_CLOEXEC)
-		// Any error means we cannot use close_range(CLOSE_RANGE_CLOEXEC).
-		// -ENOSYS and -EINVAL ultimately mean we don't have support, but any
-		// other potential error would imply that even the most basic close
-		// operation wouldn't work.
-		haveCloseRangeCloexecBool = err == nil
-	})
-	return haveCloseRangeCloexecBool
-}
-
-// 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 {
-	if haveCloseRangeCloexec() {
-		err := unix.CloseRange(uint(minFd), math.MaxUint, unix.CLOSE_RANGE_CLOEXEC)
-		return os.NewSyscallError("close_range", err)
-	}
+type fdFunc func(fd int)
 
+// fdRangeFrom calls the passed fdFunc for each file descriptor that is open in
+// the current process.
+func fdRangeFrom(minFd int, fn fdFunc) error {
 	fdDir, err := os.Open("/proc/self/fd")
 	if err != nil {
 		return err
@@ -81,17 +53,62 @@ func CloseExecFrom(minFd int) error {
 		if fd < minFd {
 			continue
 		}
-		// 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
-		// os.ReadDir did the "opendir" syscall).
-		unix.CloseOnExec(fd)
+		// Ignore the file descriptor we used for readdir, as it will be closed
+		// when we return.
+		if uintptr(fd) == fdDir.Fd() {
+			continue
+		}
+		// Run the closure.
+		fn(fd)
 	}
 	return nil
 }
 
+// CloseExecFrom sets the O_CLOEXEC flag on all file descriptors greater or
+// equal to minFd in the current process.
+func CloseExecFrom(minFd int) error {
+	return fdRangeFrom(minFd, unix.CloseOnExec)
+}
+
+//go:linkname runtime_IsPollDescriptor internal/poll.IsPollDescriptor
+
+// In order to make sure we do not close the internal epoll descriptors the Go
+// runtime uses, we need to ensure that we skip descriptors that match
+// "internal/poll".IsPollDescriptor. Yes, this is a Go runtime internal thing,
+// unfortunately there's no other way to be sure we're only keeping the file
+// descriptors the Go runtime needs. Hopefully nothing blows up doing this...
+func runtime_IsPollDescriptor(fd uintptr) bool //nolint:revive
+
+// UnsafeCloseFrom closes all file descriptors greater or equal to minFd in the
+// current process, except for those critical to Go's runtime (such as the
+// netpoll management descriptors).
+//
+// NOTE: That this function is incredibly dangerous to use in most Go code, as
+// closing file descriptors from underneath *os.File handles can lead to very
+// bad behaviour (the closed file descriptor can be re-used and then any
+// *os.File operations would apply to the wrong file). This function is only
+// intended to be called from the last stage of runc init.
+func UnsafeCloseFrom(minFd int) error {
+	// We must not close some file descriptors.
+	return fdRangeFrom(minFd, func(fd int) {
+		if runtime_IsPollDescriptor(uintptr(fd)) {
+			// These are the Go runtimes internal netpoll file descriptors.
+			// These file descriptors are operated on deep in the Go scheduler,
+			// and closing those files from underneath Go can result in panics.
+			// There is no issue with keeping them because they are not
+			// executable and are not useful to an attacker anyway. Also we
+			// don't have any choice.
+			return
+		}
+		// There's nothing we can do about errors from close(2), and the
+		// only likely error to be seen is EBADF which indicates the fd was
+		// already closed (in which case, we got what we wanted).
+		_ = unix.Close(fd)
+	})
+}
+
 // NewSockPair returns a new unix socket pair
-func NewSockPair(name string) (parent, child *os.File, err error) {
+func NewSockPair(name string) (parent *os.File, child *os.File, err error) {
 	fds, err := unix.Socketpair(unix.AF_LOCAL, unix.SOCK_STREAM|unix.SOCK_CLOEXEC, 0)
 	if err != nil {
 		return nil, nil, err