libpod: fix hang on container start and attach

When a container is attached upon start, the WaitGroup counter may
never be decremented if an error is raised before start, causing
the caller to hang.
Synchronize with the start & attach goroutine using a channel, to be
able to detect failures before start.

Signed-off-by: Marco Vedovati <mvedovati@suse.com>

1 files changed, 7 insertions, 8 deletions

diff --git a/libpod/container_attach_linux.go b/libpod/container_attach_linux.go
index 3de5ea1cf..f5aac5794 100644
--- a/libpod/container_attach_linux.go
+++ b/libpod/container_attach_linux.go
@@ -8,7 +8,6 @@ import (
 	"net"
 	"os"
 	"path/filepath"
-	"sync"
 
 	"github.com/containers/libpod/libpod/define"
 	"github.com/containers/libpod/pkg/kubeutils"
@@ -33,22 +32,22 @@ const (
 
 // Attach to the given container
 // Does not check if state is appropriate
-func (c *Container) attach(streams *AttachStreams, keys string, resize <-chan remotecommand.TerminalSize, startContainer bool, wg *sync.WaitGroup) error {
+func (c *Container) attach(streams *AttachStreams, keys string, resize <-chan remotecommand.TerminalSize, startContainer bool, started chan bool) error {
 	if !streams.AttachOutput && !streams.AttachError && !streams.AttachInput {
 		return errors.Wrapf(define.ErrInvalidArg, "must provide at least one stream to attach to")
 	}
 
 	logrus.Debugf("Attaching to container %s", c.ID())
 
-	return c.attachContainerSocket(resize, keys, streams, startContainer, wg)
+	return c.attachContainerSocket(resize, keys, streams, startContainer, started)
 }
 
 // attachContainerSocket connects to the container's attach socket and deals with the IO.
-// wg is only required if startContainer is true
+// started is only required if startContainer is true
 // TODO add a channel to allow interrupting
-func (c *Container) attachContainerSocket(resize <-chan remotecommand.TerminalSize, keys string, streams *AttachStreams, startContainer bool, wg *sync.WaitGroup) error {
-	if startContainer && wg == nil {
-		return errors.Wrapf(define.ErrInternal, "wait group not passed when startContainer set")
+func (c *Container) attachContainerSocket(resize <-chan remotecommand.TerminalSize, keys string, streams *AttachStreams, startContainer bool, started chan bool) error {
+	if startContainer && started == nil {
+		return errors.Wrapf(define.ErrInternal, "started chan not passed when startContainer set")
 	}
 
 	// Use default detach keys when keys aren't passed or specified in libpod.conf
@@ -100,7 +99,7 @@ func (c *Container) attachContainerSocket(resize <-chan remotecommand.TerminalSi
 		if err := c.start(); err != nil {
 			return err
 		}
-		wg.Done()
+		started <- true
 	}
 
 	receiveStdoutError := make(chan error)