bndiv fuzzer: limit the size of the input to avoid timeout

CLA: trivial
Reviewed-by: NEmilia Käsper <emilia@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4119)

fuzz/bndiv.c

@@ -18,6 +18,9 @@
 #include <openssl/err.h>
 #include "fuzzer.h"
 
+/* 256 kB */
+#define MAX_LEN (256 * 1000)
+
 static BN_CTX *ctx;
 static BIGNUM *b1;
 static BIGNUM *b2;
@@ -47,6 +50,10 @@ int FuzzerTestOneInput(const uint8_t *buf, size_t len)
     /* s1 and s2 will be the signs for b1 and b2. */
     int s1 = 0, s2 = 0;
 
+    /* limit the size of the input to avoid timeout */
+    if (len > MAX_LEN)
+        len = MAX_LEN;
+
     /* We are going to split the buffer in two, sizes l1 and l2, giving b1 and
      * b2.
      */