Merge pull request #633 from twpayne/allow-kernel-fail

Make reading /proc/sys/kernel more tolerant of errors

cmd/config.go

@@ -358,9 +358,10 @@ func (c *Config) getDefaultData() (map[string]interface{}, error) {
 	kernelInfo, err := getKernelInfo(c.fs)
 	if err == nil && kernelInfo != nil {
 		data["kernel"] = kernelInfo
-	} else if err != nil && !os.IsNotExist(err) {
+	} else if err != nil {
 		return nil, err
 	}
+
 	return data, nil
 }
 

cmd/data_linux.go

@@ -2,9 +2,9 @@ package cmd
 
 import (
 	"bufio"
+	"bytes"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -15,35 +15,36 @@ import (
 )
 
 func getKernelInfo(fs vfs.FS) (map[string]string, error) {
-	const procKernel = "/proc/sys/kernel"
-	files := []string{"version", "ostype", "osrelease"}
+	const procSysKernel = "/proc/sys/kernel"
 
-	stat, err := fs.Stat(procKernel)
-	if err != nil {
-		return nil, err
-	}
-	if !stat.IsDir() {
-		return nil, fmt.Errorf("expected %q to be a directory", procKernel)
+	info, err := fs.Stat(procSysKernel)
+	switch {
+	case os.IsNotExist(err):
+		return nil, nil
+	case os.IsPermission(err):
+		return nil, nil
+	case !info.Mode().IsDir():
+		return nil, nil
 	}
 
-	res := map[string]string{}
-	for _, file := range files {
-		p := filepath.Join(procKernel, file)
-		f, err := fs.Open(p)
-		if os.IsNotExist(err) {
+	kernelInfo := make(map[string]string)
+	for _, filename := range []string{
+		"osrelease",
+		"ostype",
+		"version",
+	} {
+		data, err := fs.ReadFile(filepath.Join(procSysKernel, filename))
+		switch {
+		case os.IsNotExist(err):
 			continue
-		} else if err != nil {
-			return nil, err
-		}
-		defer f.Close()
-		data, err := ioutil.ReadAll(f)
-		if err != nil {
+		case os.IsPermission(err):
+			continue
+		case err != nil:
 			return nil, err
 		}
-		res[file] = strings.TrimSpace(string(data))
+		kernelInfo[filename] = string(bytes.TrimSpace(data))
 	}
-
-	return res, nil
+	return kernelInfo, nil
 }
 
 // getOSRelease returns the operating system identification data as defined by

cmd/data_linux_test.go

@@ -10,21 +10,54 @@ import (
 )
 
 func TestGetKernelInfo(t *testing.T) {
-	root := map[string]interface{}{
-		"/proc/sys/kernel/version":   "#1 SMP Fri Nov 1 14:28:19 UTC 2019",
-		"/proc/sys/kernel/ostype":    "Linux",
-		"/proc/sys/kernel/osrelease": "4.19.81-microsoft-standard",
+	for _, tc := range []struct {
+		name               string
+		root               interface{}
+		expectedKernelInfo map[string]string
+	}{
+		{
+			name: "windows_services_for_linux",
+			root: map[string]interface{}{
+				"/proc/sys/kernel": map[string]interface{}{
+					"osrelease": "4.19.81-microsoft-standard\n",
+					"ostype":    "Linux\n",
+					"version":   "#1 SMP Debian 5.2.9-2 (2019-08-21)\n",
+				},
+			},
+			expectedKernelInfo: map[string]string{
+				"osrelease": "4.19.81-microsoft-standard",
+				"ostype":    "Linux",
+				"version":   "#1 SMP Debian 5.2.9-2 (2019-08-21)",
+			},
+		},
+		{
+			name: "debian_version_only",
+			root: map[string]interface{}{
+				"/proc/sys/kernel": map[string]interface{}{
+					"version": "#1 SMP Debian 5.2.9-2 (2019-08-21)\n",
+				},
+			},
+			expectedKernelInfo: map[string]string{
+				"version": "#1 SMP Debian 5.2.9-2 (2019-08-21)",
+			},
+		},
+		{
+			name: "proc_sys_kernel_missing",
+			root: map[string]interface{}{
+				"/proc/sys": &vfst.Dir{Perm: 0755},
+			},
+			expectedKernelInfo: nil,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			fs, cleanup, err := vfst.NewTestFS(tc.root)
+			require.NoError(t, err)
+			defer cleanup()
+			kernelInfo, err := getKernelInfo(fs)
+			assert.NoError(t, err)
+			assert.Equal(t, tc.expectedKernelInfo, kernelInfo)
+		})
 	}
-	fs, cleanup, err := vfst.NewTestFS(root)
-	require.NoError(t, err)
-	defer cleanup()
-	info, err := getKernelInfo(fs)
-	assert.NoError(t, err)
-	assert.Equal(t, map[string]string{
-		"version":   "#1 SMP Fri Nov 1 14:28:19 UTC 2019",
-		"ostype":    "Linux",
-		"osrelease": "4.19.81-microsoft-standard",
-	}, info)
 }
 
 func TestGetOSRelease(t *testing.T) {