prog: don't materialize uncompressed image in Deserialize

Currently we uncompress all images in Deserialize to check that the data is valid.
As the result deserializing all seeds we have takes ~40 seconds of real time
and ~125 seconds of CPU time. And we do this during every syz-manager start.

Don't materialize the uncompressed image.
This reduces real time to ~15 seconds and CPU time to 18 seconds (no garbage collections).
In syz-manager the benefit is even larger since garbage collections take longer (larger heap).

1 files changed, 3 insertions, 3 deletions

diff --git a/sys/linux/init_images.go b/sys/linux/init_images.go
index 0284f9190..8b62455d2 100644
--- a/sys/linux/init_images.go
+++ b/sys/linux/init_images.go
@@ -24,11 +24,11 @@ func (arch *arch) extractSyzMountImage(c *prog.Call) (io.Reader, error) {
 	} else if len(data) == 0 {
 		return nil, fmt.Errorf("an empty image")
 	}
-	decompressedData, err := prog.Decompress(data)
-	if err != nil {
+	buf := new(bytes.Buffer)
+	if err := prog.DecompressWriter(buf, data); err != nil {
 		return nil, err
 	}
-	return bytes.NewReader(decompressedData), nil
+	return buf, nil
 }
 
 func (arch *arch) fixUpSyzMountImage(c *prog.Call, fixStructure bool) error {