fix: check err returned by newGenericDecompressor

There is a couple of newGenericDecompressor function usages, where
returned possibly non-nil `err` is not checked before dereferencing
returned decompressor. It may lead to nil ptr dereferencing.

This commit adds check for `err` to prevent dereferencing potentially
nullable decompressor.

Found by Linux Verification Center (linuxtesting.org) with SVACE

Signed-off-by: Mikhail Dmitrichenko <[email protected]>

Author: Mikhail Dmitrichenko

pkg/machine/compression/uncompressed.go

@@ -10,6 +10,9 @@ type uncompressedDecompressor struct {
 
 func newUncompressedDecompressor(compressedFilePath string) (*uncompressedDecompressor, error) {
 	d, err := newGenericDecompressor(compressedFilePath)
+	if err != nil {
+		return nil, err
+	}
 	return &uncompressedDecompressor{*d}, err
 }
 

pkg/machine/compression/zip.go

@@ -16,6 +16,9 @@ type zipDecompressor struct {
 
 func newZipDecompressor(compressedFilePath string) (*zipDecompressor, error) {
 	d, err := newGenericDecompressor(compressedFilePath)
+	if err != nil {
+		return nil, err
+	}
 	return &zipDecompressor{*d, nil, nil}, err
 }