From 0ac98807c3d058f2bccd7f4ac7abdd1dbddbdbf7 Mon Sep 17 00:00:00 2001
From: Kir Kolyshkin <kolyshkin@gmail.com>
Date: Thu, 14 Apr 2022 12:19:39 -0700
Subject: [PATCH] libct/cg/sd: stop using regex, fix systemdVersionAtoi

Rewrite systemdVersionAtoi to not use regexp, and fix two issues:

1. It was returning 0 (rather than -1) for some errors.

2. The comment was saying that the input string is without quotes,
   while in fact it is.

Note the new function, similar to the old one, works on input either
with or without quotes. Amend the test to add test cases without quotes.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
---
 libcontainer/cgroups/systemd/common.go       | 27 +++++++++++---------
 libcontainer/cgroups/systemd/systemd_test.go |  7 +++--
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/libcontainer/cgroups/systemd/common.go b/libcontainer/cgroups/systemd/common.go
index 0c3562e6bfe..2f0767b2fd8 100644
--- a/libcontainer/cgroups/systemd/common.go
+++ b/libcontainer/cgroups/systemd/common.go
@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"math"
 	"os"
-	"regexp"
 	"strconv"
 	"strings"
 	"sync"
@@ -231,18 +230,22 @@ func systemdVersion(cm *dbusConnManager) int {
 	return version
 }
 
-func systemdVersionAtoi(verStr string) (int, error) {
-	// verStr should be of the form:
-	// "v245.4-1.fc32", "245", "v245-1.fc32", "245-1.fc32" (without quotes).
-	// The result for all of the above should be 245.
-	// Thus, we unconditionally remove the "v" prefix
-	// and then match on the first integer we can grab.
-	re := regexp.MustCompile(`v?([0-9]+)`)
-	matches := re.FindStringSubmatch(verStr)
-	if len(matches) < 2 {
-		return 0, fmt.Errorf("can't parse version %s: incorrect number of matches %v", verStr, matches)
+// systemdVersionAtoi extracts a numeric systemd version from the argument.
+// The argument should be of the form: "v245.4-1.fc32", "245", "v245-1.fc32",
+// "245-1.fc32" (with or without quotes). The result for all of the above
+// should be 245.
+func systemdVersionAtoi(str string) (int, error) {
+	// Unconditionally remove the leading prefix ("v).
+	str = strings.TrimLeft(str, `"v`)
+	// Match on the first integer we can grab.
+	for i := 0; i < len(str); i++ {
+		if str[i] < '0' || str[i] > '9' {
+			// First non-digit: cut the tail.
+			str = str[:i]
+			break
+		}
 	}
-	ver, err := strconv.Atoi(matches[1])
+	ver, err := strconv.Atoi(str)
 	if err != nil {
 		return -1, fmt.Errorf("can't parse version: %w", err)
 	}
diff --git a/libcontainer/cgroups/systemd/systemd_test.go b/libcontainer/cgroups/systemd/systemd_test.go
index d280a3090aa..40584f78eba 100644
--- a/libcontainer/cgroups/systemd/systemd_test.go
+++ b/libcontainer/cgroups/systemd/systemd_test.go
@@ -35,8 +35,11 @@ func TestSystemdVersion(t *testing.T) {
 		{`"v245.4-1.fc32"`, 245, false},
 		{`"241-1"`, 241, false},
 		{`"v241-1"`, 241, false},
-		{"NaN", 0, true},
-		{"", 0, true},
+		{`333.45"`, 333, false},
+		{`v321-0`, 321, false},
+		{"NaN", -1, true},
+		{"", -1, true},
+		{"v", -1, true},
 	}
 	for _, sdTest := range systemdVersionTests {
 		ver, err := systemdVersionAtoi(sdTest.verStr)