prog: fix out-of-bounds access

ParseLog can access data out-of-bounds.
Fix that and fix regression fuzz tests to catch this.

Author: dvyukov

pkg/report/report_test.go

@@ -372,6 +372,6 @@ func TestFuzz(t *testing.T) {
 		"cleaned vnod\re",
 		"kernel\r:",
 	} {
-		Fuzz([]byte(data))
+		Fuzz([]byte(data)[:len(data):len(data)])
 	}
 }

prog/parse.go

@@ -26,7 +26,7 @@ func (target *Target) ParseLog(data []byte) []*LogEntry {
 	for pos := 0; pos < len(data); {
 		nl := bytes.IndexByte(data[pos:], '\n')
 		if nl == -1 {
-			nl = len(data)
+			nl = len(data) - 1
 		} else {
 			nl += pos
 		}

prog/test/fuzz_test.go

@@ -22,9 +22,11 @@ mutate4()
 mutate7()
 mutate8()
 `,
+		`E`,
 	} {
 		t.Logf("test #%v: %q", i, data)
-		FuzzDeserialize([]byte(data))
-		FuzzParseLog([]byte(data))
+		inp := []byte(data)[:len(data):len(data)]
+		FuzzDeserialize(inp)
+		FuzzParseLog(inp)
 	}
 }