[fuzzer] Size the decompression output buffer randomly

tests/fuzz/dictionary_decompress.c

@@ -20,43 +20,42 @@
 #include "zstd_helpers.h"
 
 static ZSTD_DCtx *dctx = NULL;
-static void* rBuf = NULL;
-static size_t bufSize = 0;
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
-    FUZZ_dict_t dict;
-    size_t neededBufSize;
-
     uint32_t seed = FUZZ_seed(&src, &size);
-    neededBufSize = MAX(20 * size, (size_t)256 << 10);
+    FUZZ_dict_t dict;
+    ZSTD_DDict* ddict = NULL;
+    int i;
 
-    /* Allocate all buffers and contexts if not already allocated */
-    if (neededBufSize > bufSize) {
-        free(rBuf);
-        rBuf = malloc(neededBufSize);
-        bufSize = neededBufSize;
-        FUZZ_ASSERT(rBuf);
-    }
     if (!dctx) {
         dctx = ZSTD_createDCtx();
         FUZZ_ASSERT(dctx);
     }
     dict = FUZZ_train(src, size, &seed);
     if (FUZZ_rand32(&seed, 0, 1) == 0) {
-        ZSTD_decompress_usingDict(dctx,
+        ddict = ZSTD_createDDict(dict.buff, dict.size);
-                rBuf, neededBufSize,
+        FUZZ_ASSERT(ddict);
-                src, size,
-                dict.buff, dict.size);
     } else {
         FUZZ_ZASSERT(ZSTD_DCtx_loadDictionary_advanced(
                 dctx, dict.buff, dict.size,
                 (ZSTD_dictLoadMethod_e)FUZZ_rand32(&seed, 0, 1),
                 (ZSTD_dictContentType_e)FUZZ_rand32(&seed, 0, 2)));
-        ZSTD_decompressDCtx(dctx, rBuf, neededBufSize, src, size);
     }
-
+    /* Run it 10 times over 10 output sizes. Reuse the context and dict. */
+    for (i = 0; i < 10; ++i) {
+        size_t const bufSize = FUZZ_rand32(&seed, 0, 2 * size);
+        void* rBuf = malloc(bufSize);
+        FUZZ_ASSERT(rBuf);
+        if (ddict) {
+            ZSTD_decompress_usingDDict(dctx, rBuf, bufSize, src, size, ddict);
+        } else {
+            ZSTD_decompressDCtx(dctx, rBuf, bufSize, src, size);
+        }
+        free(rBuf);
+    }
     free(dict.buff);
+    ZSTD_freeDDict(ddict);
 #ifndef STATEFUL_FUZZING
     ZSTD_freeDCtx(dctx); dctx = NULL;
 #endif

tests/fuzz/simple_decompress.c

@@ -19,28 +19,24 @@
 #include "zstd.h"
 
 static ZSTD_DCtx *dctx = NULL;
-static void* rBuf = NULL;
-static size_t bufSize = 0;
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
-    size_t neededBufSize;
 
-    FUZZ_seed(&src, &size);
+    uint32_t seed = FUZZ_seed(&src, &size);
-    neededBufSize = MAX(20 * size, (size_t)256 << 10);
+    int i;
-
-    /* Allocate all buffers and contexts if not already allocated */
-    if (neededBufSize > bufSize) {
-        free(rBuf);
-        rBuf = malloc(neededBufSize);
-        bufSize = neededBufSize;
-        FUZZ_ASSERT(rBuf);
-    }
     if (!dctx) {
         dctx = ZSTD_createDCtx();
         FUZZ_ASSERT(dctx);
     }
-    ZSTD_decompressDCtx(dctx, rBuf, neededBufSize, src, size);
+    /* Run it 10 times over 10 output sizes. Reuse the context. */
+    for (i = 0; i < 10; ++i) {
+        size_t const bufSize = FUZZ_rand32(&seed, 0, 2 * size);
+        void* rBuf = malloc(bufSize);
+        FUZZ_ASSERT(rBuf);
+        ZSTD_decompressDCtx(dctx, rBuf, bufSize, src, size);
+        free(rBuf);
+    }
 
 #ifndef STATEFUL_FUZZING
     ZSTD_freeDCtx(dctx); dctx = NULL;