runc run/exec: fix terminal wrt stdin redirection

This fixes the following failure:

> sudo runc run -b bundle ctr </dev/null
> WARN[0000] exit status 2
> ERRO[0000] container_linux.go:367: starting container process caused: process_linux.go:459: container init caused:

The "exit status 2" with no error message is most probably caused
by the panic in console.Current(), and is addressed by [1].

Otherwise, the issue here is simple: the code assumes stdin
is opened to a terminal, and fails to work otherwise. Some
standard Linux tools (e.g. stty, top) do the same (modulo panic),
while some others (reset, tput) use the trick of trying
all the three std streams (starting with stderr as it is least likely
to be redirected), and if all three fails, open /dev/tty.

This commit does the same, except that /dev/tty is not tried.
It also replaces the call to console.Current() which might
panic by reusing the t.hostConsole.

Fixes: opencontainers#2485

[1] containerd/console#37

Signed-off-by: Kir Kolyshkin <[email protected]>

tty.go

@@ -12,16 +12,17 @@ import (
 	"github.com/containerd/console"
 	"github.com/opencontainers/runc/libcontainer"
 	"github.com/opencontainers/runc/libcontainer/utils"
+	"github.com/pkg/errors"
 )
 
 type tty struct {
-	epoller   *console.Epoller
-	console   *console.EpollConsole
-	stdin     console.Console
-	closers   []io.Closer
-	postStart []io.Closer
-	wg        sync.WaitGroup
-	consoleC  chan error
+	epoller     *console.Epoller
+	console     *console.EpollConsole
+	hostConsole console.Console
+	closers     []io.Closer
+	postStart   []io.Closer
+	wg          sync.WaitGroup
+	consoleC    chan error
 }
 
 func (t *tty) copyIO(w io.Writer, r io.ReadCloser) {
@@ -99,18 +100,32 @@ func (t *tty) recvtty(process *libcontainer.Process, socket *os.File) (Err error
 	t.wg.Add(1)
 	go t.copyIO(os.Stdout, epollConsole)
 
-	// set raw mode to stdin and also handle interrupt
-	stdin, err := console.ConsoleFromFile(os.Stdin)
-	if err != nil {
-		return err
+	// Set raw mode for the controlling terminal. Usually all three
+	// (stdin, stdout, and stderr) streams are open to the terminal,
+	// but they might be redirected, so try them all.
+	var hostConsole console.Console
+	for _, s := range []*os.File{os.Stderr, os.Stdout, os.Stdin} {
+		c, err := console.ConsoleFromFile(s)
+		switch err {
+		case console.ErrNotAConsole:
+			continue
+		case nil:
+			hostConsole = c
+		default:
+			return errors.Wrap(err, "unable to get console")
+		}
 	}
-	if err := stdin.SetRaw(); err != nil {
+	if hostConsole == nil {
+		return errors.New("unable to find console (are all streams redirected?)")
+	}
+
+	if err := hostConsole.SetRaw(); err != nil {
 		return fmt.Errorf("failed to set the terminal from the stdin: %v", err)
 	}
-	go handleInterrupt(stdin)
+	go handleInterrupt(hostConsole)
 
 	t.epoller = epoller
-	t.stdin = stdin
+	t.hostConsole = hostConsole
 	t.console = epollConsole
 	t.closers = []io.Closer{epollConsole}
 	return nil
@@ -156,8 +171,8 @@ func (t *tty) Close() error {
 	for _, c := range t.closers {
 		c.Close()
 	}
-	if t.stdin != nil {
-		t.stdin.Reset()
+	if t.hostConsole != nil {
+		t.hostConsole.Reset()
 	}
 	return nil
 }
@@ -166,5 +181,5 @@ func (t *tty) resize() error {
 	if t.console == nil {
 		return nil
 	}
-	return t.console.ResizeFrom(console.Current())
+	return t.console.ResizeFrom(t.hostConsole)
 }