Zero out FIPS counters.

MSAN doesn't like the counters starting at whatever value malloc
found to be free.

Change-Id: I0968e61e0025db35b82291fde5d1e193aef77c1e
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/46444
Commit-Queue: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

crypto/fipsmodule/self_check/fips.c

diff --git a/crypto/fipsmodule/self_check/fips.c b/crypto/fipsmodule/self_check/fips.c
index 09fffdd..d55c493 100644
--- a/crypto/fipsmodule/self_check/fips.c
+++ b/crypto/fipsmodule/self_check/fips.c
@@ -52,10 +52,13 @@
   size_t *array =
       CRYPTO_get_thread_local(OPENSSL_THREAD_LOCAL_FIPS_COUNTERS);
   if (!array) {
-    array = OPENSSL_malloc(sizeof(size_t) * (fips_counter_max + 1));
+    const size_t num_bytes = sizeof(size_t) * (fips_counter_max + 1);
+    array = OPENSSL_malloc(num_bytes);
     if (!array) {
       return;
     }
+
+    OPENSSL_memset(array, 0, num_bytes);
     if (!CRYPTO_set_thread_local(OPENSSL_THREAD_LOCAL_FIPS_COUNTERS, array,
                                  OPENSSL_free)) {
       // |OPENSSL_free| has already been called by |CRYPTO_set_thread_local|.