Fix maxmemory-samples stack overflow crash in evictionPoolPopulate, l…

…imit its value to [1,64]

We have not limited the value of maxmemory-samples in the past, it can
be set very large. If it is set very large, we will have stack overflow
in evictionPoolPopulate when we trigger the key eviction.

There is no reason for this config to be set too high, so just limit its
range to [1,64].

redis.conf

@@ -1163,7 +1163,8 @@ acllog-max-len 128
 # configuration directive.
 #
 # The default of 5 produces good enough results. 10 Approximates very closely
-# true LRU but costs more CPU. 3 is faster but not very accurate.
+# true LRU but costs more CPU. 3 is faster but not very accurate. The maximum
+# value that can be set is 64.
 #
 # maxmemory-samples 5
 

src/config.c

@@ -3172,7 +3172,7 @@ standardConfig static_configs[] = {
     createIntConfig("lfu-decay-time", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, server.lfu_decay_time, 1, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("replica-priority", "slave-priority", MODIFIABLE_CONFIG, 0, INT_MAX, server.slave_priority, 100, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("repl-diskless-sync-delay", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, server.repl_diskless_sync_delay, 5, INTEGER_CONFIG, NULL, NULL),
-    createIntConfig("maxmemory-samples", NULL, MODIFIABLE_CONFIG, 1, INT_MAX, server.maxmemory_samples, 5, INTEGER_CONFIG, NULL, NULL),
+    createIntConfig("maxmemory-samples", NULL, MODIFIABLE_CONFIG, 1, 64, server.maxmemory_samples, 5, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("maxmemory-eviction-tenacity", NULL, MODIFIABLE_CONFIG, 0, 100, server.maxmemory_eviction_tenacity, 10, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("timeout", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, server.maxidletime, 0, INTEGER_CONFIG, NULL, NULL), /* Default client timeout: infinite */
     createIntConfig("replica-announce-port", "slave-announce-port", MODIFIABLE_CONFIG, 0, 65535, server.slave_announce_port, 0, INTEGER_CONFIG, NULL, NULL),