Two fixes for ghostcript (#2562)

* [ghostscript] Fix ininitialized pointer

Passing an invalid pointer causes a crash in gs_new_instance.

* [ghostscript] Add seed corpus

Use the examples distributed with ghostcript as a seed corpus.

projects/ghostscript/build.sh

@@ -54,3 +54,10 @@ $CXX $CXXFLAGS $CUPS_LDFLAGS -std=c++11 -I. \
     -o "$OUT/gstoraster_fuzzer" \
     $CUPS_LIBS \
     $LIB_FUZZING_ENGINE bin/gs.a
+
+mkdir -p "$WORK/seeds"
+for f in examples/*.{ps,pdf}; do
+  s=$(sha1sum "$f" | awk '{print $1}')
+  cp "$f" "$WORK/seeds/$s"
+done
+zip -j "$OUT/gstoraster_fuzzer_seed_corpus.zip" "$WORK"/seeds/*

projects/ghostscript/gstoraster_fuzzer.cc

@@ -37,7 +37,7 @@ static int gs_stdout(void *inst, const char *buf, int len)
 static int gs_to_raster_fuzz(const unsigned char *buf, size_t size)
 {
 	int ret;
-	void *gs;
+	void *gs = NULL;
 
 	/* Mostly stolen from cups-filters gstoraster. */
 	char *args[] = {