Lagom: Add a PPM fuzzer

It finds the problem fixed in 69518bd178ebfaa but nothing else.

Meta/Lagom/Fuzzers/CMakeLists.txt

@@ -25,6 +25,15 @@ target_link_libraries(FuzzGemini
     PRIVATE $<$<C_COMPILER_ID:Clang>:-fsanitize=fuzzer>
     )
 
+add_executable(FuzzPPMLoader FuzzPPMLoader.cpp)
+target_compile_options(FuzzPPMLoader
+    PRIVATE $<$<C_COMPILER_ID:Clang>:-g -O1 -fsanitize=fuzzer>
+    )
+target_link_libraries(FuzzPPMLoader
+    PUBLIC Lagom
+    PRIVATE $<$<C_COMPILER_ID:Clang>:-fsanitize=fuzzer>
+    )
+
 add_executable(FuzzJs FuzzJs.cpp)
 target_compile_options(FuzzJs
     PRIVATE $<$<C_COMPILER_ID:Clang>:-g -O1 -fsanitize=fuzzer>

Meta/Lagom/Fuzzers/FuzzPPMLoader.cpp

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibGfx/PPMLoader.h>
+#include <stddef.h>
+#include <stdint.h>
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
+{
+    Gfx::load_ppm_from_memory(data, size);
+    return 0;
+}