Merge pull request #45641 from cpuguy83/exec_npe

Fix npe in exec resize when exec errored

daemon/resize.go

@@ -5,6 +5,8 @@ import (
 	"errors"
 	"strconv"
 	"time"
+
+	"github.com/docker/docker/errdefs"
 )
 
 // ContainerResize changes the size of the TTY of the process running
@@ -48,6 +50,10 @@ func (daemon *Daemon) ContainerExecResize(name string, height, width int) error
 
 	select {
 	case <-ec.Started:
+		// An error may have occurred, so ec.Process may be nil.
+		if ec.Process == nil {
+			return errdefs.InvalidParameter(errors.New("exec process is not started"))
+		}
 		return ec.Process.Resize(context.Background(), uint32(width), uint32(height))
 	case <-timeout.C:
 		return errors.New("timeout waiting for exec session ready")