[fuzz] Add a compression fuzzer with randomly sized output buffer (#1670)

tests/fuzz/simple_compress.c

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ */
+
+/**
+ * This fuzz target attempts to comprss the fuzzed data with the simple
+ * compression function with an output buffer that may be too small to
+ * ensure that the compressor never crashes.
+ */
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include "fuzz_helpers.h"
+#include "zstd.h"
+
+static ZSTD_CCtx *cctx = NULL;
+
+int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
+{
+    uint32_t seed = FUZZ_seed(&src, &size);
+    size_t const maxSize = ZSTD_compressBound(size);
+    int i;
+    if (!cctx) {
+        cctx = ZSTD_createCCtx();
+        FUZZ_ASSERT(cctx);
+    }
+    /* Run it 10 times over 10 output sizes. Reuse the context. */
+    for (i = 0; i < 10; ++i) {
+        int const level = (int)FUZZ_rand32(&seed, 0, 19 + 3) - 3; /* [-3, 19] */
+        size_t const bufSize = FUZZ_rand32(&seed, 0, maxSize);
+        void* rBuf = malloc(bufSize);
+        FUZZ_ASSERT(rBuf);
+        ZSTD_compressCCtx(cctx, rBuf, bufSize, src, size, level);
+        free(rBuf);
+    }
+
+#ifndef STATEFUL_FUZZING
+    ZSTD_freeCCtx(cctx); cctx = NULL;
+#endif
+    return 0;
+}