Fix possible integer overflow in memory allocation with negative precision in geohash_encode

Author: emirb

geohash.c

@@ -48,6 +48,10 @@ char *php_geo_geohash_encode(double latitude, double longitude, int precision)
 	interval_struct  lng_interval = { MAX_LONG, MIN_LONG };
 	interval_struct *interval;
 
+        if (precision < 0) {
+            precision = 0;
+        }
+
 	hash = (char*)safe_emalloc(precision, sizeof(char), 1);
 
 	hash[precision] = '\0';

tests/geohash_encode.phpt

@@ -11,6 +11,7 @@ echo geohash_encode(array('type' => 'Point', 'coordinates' => [95, 95]), 6).PHP_
 echo geohash_encode(array('type' => 'Point', 'coordinates' => [185, 185]), 12).PHP_EOL;
 echo geohash_encode(array('type' => 'Point', 'coordinates' => [-90, -185]), 12).PHP_EOL;
 echo var_dump(geohash_encode(array('type' => 'Point', 'coordinates' => [30, 30]), 0));
+echo var_dump(geohash_encode(array('type' => 'Point', 'coordinates' => [30, 30]), -1));
 ?>
 --EXPECT--
 u2edjnw17enr
@@ -20,3 +21,4 @@ ypgxcz
 zzzzzzzzzzzz
 1bpbpbpbpbpb
 string(0) ""
+string(0) ""