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 caused by SIGHUP
which is sent to init by the kernel when we are losing the
controlling terminal. If we choose to ignore that, we'll get
panic in console.Current(), which 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 a similar thing (see initHostConsole).

It also replaces the call to console.Current(), which may panic
(see [1]), by reusing the t.hostConsole.

Finally, a simple test case is added.

Fixes: https://github.com/opencontainers/runc/issues/2485

[1] https://github.com/containerd/console/pull/37

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

utils_linux.go

@@ -157,6 +157,9 @@ func setupIO(process *libcontainer.Process, rootuid, rootgid int, createTTY, det
 		process.Stderr = nil
 		t := &tty{}
 		if !detach {
+			if err := t.initHostConsole(); err != nil {
+				return nil, err
+			}
 			parent, child, err := utils.NewSockPair("console")
 			if err != nil {
 				return nil, err