From a4b90be9fcd5e1668ac941cabce3b1ab38dbe326 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Fri, 15 Mar 2019 17:10:16 +0100
Subject: [PATCH] HyperLogLog: enlarge reghisto variable for safety.

---
 src/hyperloglog.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/hyperloglog.c b/src/hyperloglog.c
index e993bf26e1d..526510b43b9 100644
--- a/src/hyperloglog.c
+++ b/src/hyperloglog.c
@@ -1017,7 +1017,12 @@ uint64_t hllCount(struct hllhdr *hdr, int *invalid) {
     double m = HLL_REGISTERS;
     double E;
     int j;
-    int reghisto[HLL_Q+2] = {0};
+    /* Note that reghisto could be just HLL_Q+1, becuase this is the
+     * maximum frequency of the "000...1" sequence the hash function is
+     * able to return. However it is slow to check for sanity of the
+     * input: instead we history array at a safe size: overflows will
+     * just write data to wrong, but correctly allocated, places. */
+    int reghisto[64] = {0};
 
     /* Compute register histogram */
     if (hdr->encoding == HLL_DENSE) {