The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/b19ef813adca6ad2ad1af1905fe0e7b5c1603476

commit b19ef813adca6ad2ad1af1905fe0e7b5c1603476
Author: Stephen Barber <smbarber@chromium.org>
Date: Thu Sep 20 12:15:20 2018

vm_tools: vsh: handle EOF from client

Update VshClient to forward EOF from stdin to vshd, and to stop
polling stdin after reaching EOF. VshClient must still remain active
to print output from vshd.

Also update VshForwarder to interpret a zero-length data message as EOF,
and forward that to the target process via the tty driver.

BUG= chromium:885255 
TEST=repro case in bug

Change-Id: If8b0e8449418b13fd82a792ee13d6541f4da8044
Reviewed-on: https://chromium-review.googlesource.com/1232935
Commit-Ready: Stephen Barber <smbarber@chromium.org>
Tested-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Jeffrey Kardatzke <jkardatzke@google.com>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>

[modify] https://crrev.com/b19ef813adca6ad2ad1af1905fe0e7b5c1603476/vm_tools/vsh/vsh_forwarder.cc
[modify] https://crrev.com/b19ef813adca6ad2ad1af1905fe0e7b5c1603476/vm_tools/vsh/vsh_client.cc
[modify] https://crrev.com/b19ef813adca6ad2ad1af1905fe0e7b5c1603476/vm_tools/vsh/vsh_client.h

Fixed, preparing a new component with this change now.

Both the component and host need to be updated before the echo command above will work.

I'm not sure whether it's still the issue. But I encountered some problem while trying to fix the issue in 
https://cs.corp.google.com/chromeos_public/src/platform/tast-tests/src/chromiumos/tast/local/vm/container.go?type=cs&q=PushFile+file:%5Esrc/platform/tast-tests/src/chromiumos/tast/+package:%5Echromeos_public$&g=0&l=214

The original code doesn't work well because I need to copy a file whose size exceeds shell ARG_MAX. I tried to feed the payload to vsh via stdin, but the following code hang forever. It looks vsh couldn't get data from stdin or EOF is not handled correctly.

        args := []string{"--vm_name=" + c.VM.name,
                "--target_container=" + c.containerName,
                "--owner_id=" + c.VM.Concierge.ownerID,
                "--", "sh", "-c", "base64 --decode >"+containerPath}
        cmd := testexec.CommandContext(ctx, "vsh", args...)
        cmd.Stdin = bytes.NewBufferString(base64Data)
        testing.ContextLog(ctx, "Before running cmd.Run()")
        err = cmd.Run()
        if err != nil {
                cmd.DumpLog(ctx)
                return err
        }
        testing.ContextLog(ctx, "After running cmd.Run()")

However, doing it on the host via shell works
$ base64 /usr/local/bin/sysbench | vsh --vm_name=termina --target_container=penguin --owner_id=2c5859c2a92932288ce902f6c2a0746270229178 -- sh -c 'base64 --decode >/home/testuser/sysbench'

Here's a patch to reproduce the problem:
https://chromium-review.googlesource.com/c/chromiumos/platform/tast-tests/+/1423958