From 0af5cd204103a23b047bd4b8e4159f8ef5a1ef3c Mon Sep 17 00:00:00 2001
From: Kir Kolyshkin <kolyshkin@gmail.com>
Date: Fri, 27 Mar 2020 00:10:53 -0700
Subject: [PATCH 1/2] Nit: fix use of bufio.Scanner.Err

The Err() method should be called after the Scan() loop, not inside it.

Found by

 git grep -A3 -F '.Scan()' | grep Err

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
---
 libcontainer/cgroups/fs2/defaultpath.go |  6 +++---
 libcontainer/intelrdt/intelrdt.go       |  8 +++----
 libcontainer/user/user.go               | 28 +++++++++++--------------
 3 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/libcontainer/cgroups/fs2/defaultpath.go b/libcontainer/cgroups/fs2/defaultpath.go
index e84b33f2c..3d1fec336 100644
--- a/libcontainer/cgroups/fs2/defaultpath.go
+++ b/libcontainer/cgroups/fs2/defaultpath.go
@@ -80,9 +80,6 @@ func parseCgroupFromReader(r io.Reader) (string, error) {
 		s = bufio.NewScanner(r)
 	)
 	for s.Scan() {
-		if err := s.Err(); err != nil {
-			return "", err
-		}
 		var (
 			text  = s.Text()
 			parts = strings.SplitN(text, ":", 3)
@@ -95,5 +92,8 @@ func parseCgroupFromReader(r io.Reader) (string, error) {
 			return parts[2], nil
 		}
 	}
+	if err := s.Err(); err != nil {
+		return "", err
+	}
 	return "", errors.New("cgroup path not found")
 }
diff --git a/libcontainer/intelrdt/intelrdt.go b/libcontainer/intelrdt/intelrdt.go
index 30eca4dc8..c77de8845 100644
--- a/libcontainer/intelrdt/intelrdt.go
+++ b/libcontainer/intelrdt/intelrdt.go
@@ -310,10 +310,6 @@ func parseCpuInfoFile(path string) (bool, bool, error) {
 
 	s := bufio.NewScanner(f)
 	for s.Scan() {
-		if err := s.Err(); err != nil {
-			return false, false, err
-		}
-
 		line := s.Text()
 
 		// Search "cat_l3" and "mba" flags in first "flags" line
@@ -331,6 +327,10 @@ func parseCpuInfoFile(path string) (bool, bool, error) {
 			return isCatFlagSet, isMbaFlagSet, nil
 		}
 	}
+	if err := s.Err(); err != nil {
+		return false, false, err
+	}
+
 	return isCatFlagSet, isMbaFlagSet, nil
 }
 
diff --git a/libcontainer/user/user.go b/libcontainer/user/user.go
index 7b912bbf8..de30982ba 100644
--- a/libcontainer/user/user.go
+++ b/libcontainer/user/user.go
@@ -162,10 +162,6 @@ func ParsePasswdFilter(r io.Reader, filter func(User) bool) ([]User, error) {
 	)
 
 	for s.Scan() {
-		if err := s.Err(); err != nil {
-			return nil, err
-		}
-
 		line := strings.TrimSpace(s.Text())
 		if line == "" {
 			continue
@@ -183,6 +179,9 @@ func ParsePasswdFilter(r io.Reader, filter func(User) bool) ([]User, error) {
 			out = append(out, p)
 		}
 	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
 
 	return out, nil
 }
@@ -221,10 +220,6 @@ func ParseGroupFilter(r io.Reader, filter func(Group) bool) ([]Group, error) {
 	)
 
 	for s.Scan() {
-		if err := s.Err(); err != nil {
-			return nil, err
-		}
-
 		text := s.Text()
 		if text == "" {
 			continue
@@ -242,6 +237,9 @@ func ParseGroupFilter(r io.Reader, filter func(Group) bool) ([]Group, error) {
 			out = append(out, p)
 		}
 	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
 
 	return out, nil
 }
@@ -532,10 +530,6 @@ func ParseSubIDFilter(r io.Reader, filter func(SubID) bool) ([]SubID, error) {
 	)
 
 	for s.Scan() {
-		if err := s.Err(); err != nil {
-			return nil, err
-		}
-
 		line := strings.TrimSpace(s.Text())
 		if line == "" {
 			continue
@@ -549,6 +543,9 @@ func ParseSubIDFilter(r io.Reader, filter func(SubID) bool) ([]SubID, error) {
 			out = append(out, p)
 		}
 	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
 
 	return out, nil
 }
@@ -586,10 +583,6 @@ func ParseIDMapFilter(r io.Reader, filter func(IDMap) bool) ([]IDMap, error) {
 	)
 
 	for s.Scan() {
-		if err := s.Err(); err != nil {
-			return nil, err
-		}
-
 		line := strings.TrimSpace(s.Text())
 		if line == "" {
 			continue
@@ -603,6 +596,9 @@ func ParseIDMapFilter(r io.Reader, filter func(IDMap) bool) ([]IDMap, error) {
 			out = append(out, p)
 		}
 	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
 
 	return out, nil
 }

From aab2c8ba52d9c66cda63017fd35c0b3918d1d592 Mon Sep 17 00:00:00 2001
From: Kir Kolyshkin <kolyshkin@gmail.com>
Date: Fri, 27 Mar 2020 00:31:26 -0700
Subject: [PATCH 2/2] libcontainer/intelrdt: optimize parseCpuInfoFile

The line we are parsing looks like this

> flags		: fpu vme de pse <...>

so look for "flags" as a prefix, not substring.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
---
 libcontainer/intelrdt/intelrdt.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libcontainer/intelrdt/intelrdt.go b/libcontainer/intelrdt/intelrdt.go
index c77de8845..b19580f1c 100644
--- a/libcontainer/intelrdt/intelrdt.go
+++ b/libcontainer/intelrdt/intelrdt.go
@@ -313,7 +313,7 @@ func parseCpuInfoFile(path string) (bool, bool, error) {
 		line := s.Text()
 
 		// Search "cat_l3" and "mba" flags in first "flags" line
-		if strings.Contains(line, "flags") {
+		if strings.HasPrefix(line, "flags") {
 			flags := strings.Split(line, " ")
 			// "cat_l3" flag for CAT and "mba" flag for MBA
 			for _, flag := range flags {