Fix libmagic buffer overflow issue (CVE-2019-18218)

Ported from file/file@46a8443

Author: smalyshev

ext/fileinfo/libmagic/cdf.c

@@ -872,8 +872,9 @@ cdf_read_property_info(const cdf_stream_t *sst, const cdf_header_t *h,
 		    i, inp[i].pi_id, inp[i].pi_type, q - p, offs));
 		if (inp[i].pi_type & CDF_VECTOR) {
 			nelements = CDF_GETUINT32(q, 1);
-			if (nelements == 0) {
-				DPRINTF(("CDF_VECTOR with nelements == 0\n"));
+			if (nelements > CDF_ELEMENT_LIMIT || nelements == 0) {
+				DPRINTF(("CDF_VECTOR with nelements == %"
+				    SIZE_T_FORMAT "u\n", nelements));
 				goto out;
 			}
 			o = 2;
@@ -948,8 +949,6 @@ cdf_read_property_info(const cdf_stream_t *sst, const cdf_header_t *h,
 				*info = inp;
 				inp = *info + nelem;
 			}
-			DPRINTF(("nelements = %" SIZE_T_FORMAT "u\n",
-			    nelements));
 			for (j = 0; j < nelements && i < sh.sh_properties;
 			    j++, i++)
 			{

ext/fileinfo/libmagic/cdf.h

@@ -50,6 +50,7 @@
 typedef int32_t cdf_secid_t;
 
 #define CDF_LOOP_LIMIT					10000
+#define CDF_ELEMENT_LIMIT				100000
 
 #define CDF_SECID_NULL					0
 #define CDF_SECID_FREE					-1