Toolkit: Add missing flock calls. (microsoft#10804)

When making changes to partitions or filesystems, it is recommended to take a file lock over the disk block device as this informs the host OS that you are making changes and that it should avoid scanning or changing the device until you are done. While most of the relevant operations are covered, there a few places that are missing the lock. For example, when calling `mkfs` or `resize2fs`.

toolkit/tools/imagegen/diskutils/diskutils.go

@@ -492,7 +492,7 @@ func CreatePartitions(diskDevPath string, disk configuration.Disk, rootEncryptio
 			return partDevPathMap, partIDToFsTypeMap, encryptedRoot, readOnlyRoot, err
 		}
 
-		partFsType, err := FormatSinglePartition(partDevPath, partition)
+		partFsType, err := formatSinglePartition(diskDevPath, partDevPath, partition)
 		if err != nil {
 			err = fmt.Errorf("failed to format partition:\n%w", err)
 			return partDevPathMap, partIDToFsTypeMap, encryptedRoot, readOnlyRoot, err
@@ -782,12 +782,13 @@ func setGptPartitionType(partition configuration.Partition, timeoutInSeconds, di
 	return
 }
 
-// FormatSinglePartition formats the given partition to the type specified in the partition configuration
-func FormatSinglePartition(partDevPath string, partition configuration.Partition,
+// formatSinglePartition formats the given partition to the type specified in the partition configuration
+func formatSinglePartition(diskDevPath string, partDevPath string, partition configuration.Partition,
 ) (fsType string, err error) {
 	const (
-		totalAttempts = 5
-		retryDuration = time.Second
+		totalAttempts    = 5
+		retryDuration    = time.Second
+		timeoutInSeconds = "5"
 	)
 
 	fsType = partition.FsType
@@ -803,14 +804,14 @@ func FormatSinglePartition(partDevPath string, partition configuration.Partition
 			fsType = "vfat"
 		}
 
-		mkfsArgs := []string{"-t", fsType}
+		mkfsArgs := []string{"--timeout", timeoutInSeconds, diskDevPath, "mkfs", "-t", fsType}
 		mkfsArgs = append(mkfsArgs, mkfsOptions...)
 		mkfsArgs = append(mkfsArgs, partDevPath)
 
 		err = retry.Run(func() error {
-			_, stderr, err := shell.Execute("mkfs", mkfsArgs...)
+			_, stderr, err := shell.Execute("flock", mkfsArgs...)
 			if err != nil {
-				logger.Log.Warnf("Failed to format partition using mkfs: %v", stderr)
+				logger.Log.Warnf("Failed to format partition using mkfs (and flock): %v", stderr)
 				return err
 			}
 

toolkit/tools/pkg/imagecustomizerlib/shrinkfilesystems.go

@@ -85,9 +85,10 @@ func shrinkFilesystems(imageLoopDevice string, verityHashPartition *imagecustomi
 		}
 
 		// Shrink the file system with resize2fs -M
-		stdout, stderr, err := shell.Execute("resize2fs", "-M", partitionLoopDevice)
+		stdout, stderr, err := shell.Execute("flock", "--timeout", "5", imageLoopDevice,
+			"resize2fs", "-M", partitionLoopDevice)
 		if err != nil {
-			return fmt.Errorf("failed to resize %s with resize2fs:\n%v", partitionLoopDevice, stderr)
+			return fmt.Errorf("failed to resize %s with resize2fs (and flock):\n%v", partitionLoopDevice, stderr)
 		}
 
 		// Find the new partition end value
@@ -103,10 +104,11 @@ func shrinkFilesystems(imageLoopDevice string, verityHashPartition *imagecustomi
 		}
 
 		// Resize the partition with parted resizepart
-		_, stderr, err = shell.ExecuteWithStdin("yes" /*stdin*/, "parted", "---pretend-input-tty",
-			imageLoopDevice, "resizepart", strconv.Itoa(partitionNumber), end)
+		_, stderr, err = shell.ExecuteWithStdin("yes" /*stdin*/, "flock", "--timeout", "5", imageLoopDevice,
+			"parted", "---pretend-input-tty", imageLoopDevice, "resizepart",
+			strconv.Itoa(partitionNumber), end)
 		if err != nil {
-			return fmt.Errorf("failed to resizepart %s with parted:\n%v", partitionLoopDevice, stderr)
+			return fmt.Errorf("failed to resizepart %s with parted (and flock):\n%v", partitionLoopDevice, stderr)
 		}
 
 		// Re-read the partition table