From e96ac2040db90a7d9e4225b78ccc6bff373f8aeb Mon Sep 17 00:00:00 2001
From: Peter Wagner <git@mycloudand.me>
Date: Thu, 28 Mar 2019 12:59:48 -0700
Subject: [PATCH 1/2] runtime: log IO error when copying output streams

Signed-off-by: Peter Wagner <thepwagner@github.com>
---
 runtime/v1/linux/proc/io.go | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/runtime/v1/linux/proc/io.go b/runtime/v1/linux/proc/io.go
index b37c3c6aa..34f6800e2 100644
--- a/runtime/v1/linux/proc/io.go
+++ b/runtime/v1/linux/proc/io.go
@@ -29,6 +29,7 @@ import (
 	"sync"
 	"syscall"
 
+	"github.com/containerd/containerd/log"
 	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/runtime/proc"
 	"github.com/containerd/fifo"
@@ -136,7 +137,9 @@ func copyPipes(ctx context.Context, rio runc.IO, stdin, stdout, stderr string, w
 					cwg.Done()
 					p := bufPool.Get().(*[]byte)
 					defer bufPool.Put(p)
-					io.CopyBuffer(wc, rio.Stdout(), *p)
+					if _, err := io.CopyBuffer(wc, rio.Stdout(), *p); err != nil {
+						log.G(ctx).Warn("error copying stdout")
+					}
 					wg.Done()
 					wc.Close()
 					if rc != nil {
@@ -153,7 +156,9 @@ func copyPipes(ctx context.Context, rio runc.IO, stdin, stdout, stderr string, w
 					cwg.Done()
 					p := bufPool.Get().(*[]byte)
 					defer bufPool.Put(p)
-					io.CopyBuffer(wc, rio.Stderr(), *p)
+					if _, err := io.CopyBuffer(wc, rio.Stderr(), *p); err != nil {
+						log.G(ctx).Warn("error copying stderr")
+					}
 					wg.Done()
 					wc.Close()
 					if rc != nil {

From ae04c16607840a4d4977d9db19057ca74cfd4762 Mon Sep 17 00:00:00 2001
From: Peter Wagner <git@mycloudand.me>
Date: Thu, 28 Mar 2019 13:34:32 -0700
Subject: [PATCH 2/2] runtime: guard Close() until both streams are complete

Signed-off-by: Peter Wagner <thepwagner@github.com>
---
 runtime/v1/linux/proc/io.go | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/runtime/v1/linux/proc/io.go b/runtime/v1/linux/proc/io.go
index 34f6800e2..15f6ed8ca 100644
--- a/runtime/v1/linux/proc/io.go
+++ b/runtime/v1/linux/proc/io.go
@@ -27,6 +27,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"sync"
+	"sync/atomic"
 	"syscall"
 
 	"github.com/containerd/containerd/log"
@@ -123,7 +124,7 @@ func createIO(ctx context.Context, id string, ioUID, ioGID int, stdio proc.Stdio
 }
 
 func copyPipes(ctx context.Context, rio runc.IO, stdin, stdout, stderr string, wg, cwg *sync.WaitGroup) error {
-	var sameFile io.WriteCloser
+	var sameFile *countingWriteCloser
 	for _, i := range []struct {
 		name string
 		dest func(wc io.WriteCloser, rc io.Closer)
@@ -185,6 +186,7 @@ func copyPipes(ctx context.Context, rio runc.IO, stdin, stdout, stderr string, w
 			}
 		} else {
 			if sameFile != nil {
+				sameFile.count++
 				i.dest(sameFile, nil)
 				continue
 			}
@@ -192,7 +194,10 @@ func copyPipes(ctx context.Context, rio runc.IO, stdin, stdout, stderr string, w
 				return fmt.Errorf("containerd-shim: opening %s failed: %s", i.name, err)
 			}
 			if stdout == stderr {
-				sameFile = fw
+				sameFile = &countingWriteCloser{
+					WriteCloser: fw,
+					count:       1,
+				}
 			}
 		}
 		i.dest(fw, fr)
@@ -217,6 +222,19 @@ func copyPipes(ctx context.Context, rio runc.IO, stdin, stdout, stderr string, w
 	return nil
 }
 
+// countingWriteCloser masks io.Closer() until close has been invoked a certain number of times.
+type countingWriteCloser struct {
+	io.WriteCloser
+	count int64
+}
+
+func (c *countingWriteCloser) Close() error {
+	if atomic.AddInt64(&c.count, -1) > 0 {
+		return nil
+	}
+	return c.WriteCloser.Close()
+}
+
 // isFifo checks if a file is a fifo
 // if the file does not exist then it returns false
 func isFifo(path string) (bool, error) {