Fix most obvious intel-microcode2ucode buffer overruns.
Index: microcode_ctl-2.1-19/intel-microcode2ucode.c
===================================================================
--- microcode_ctl-2.1-19.orig/intel-microcode2ucode.c	2018-08-20 04:32:26.803450076 +0200
+++ microcode_ctl-2.1-19/intel-microcode2ucode.c	2018-08-20 04:33:49.324661025 +0200
@@ -47,16 +47,25 @@
 	char c[0];
 };
 
+#define MAX_MICROCODE 4000000
+
 int main(int argc, char *argv[])
 {
 	char *filename = "/lib/firmware/microcode.dat";
 	FILE *input, *f;
 	char line[LINE_MAX];
-	char buf[4000000];
+	char *buf = NULL;
 	union mcbuf *mc;
 	size_t bufsize, count, start;
 	int rc = EXIT_SUCCESS;
 
+	buf = malloc(MAX_MICROCODE);
+	if (!buf) {
+		printf("can't allocate buffer\n");
+		rc = EXIT_FAILURE;
+		goto out;
+	}
+
 	if (argv[1] != NULL)
 		filename = argv[1];
 
@@ -74,6 +83,12 @@
 	count = 0;
 	mc = (union mcbuf *) buf;
 	while (fgets(line, sizeof(line), input) != NULL) {
+		if ((count + 3) >= (MAX_MICROCODE / sizeof(mc->i[0]))) {
+			printf("input file is too big");
+			rc = EXIT_FAILURE;
+			goto out;
+		}
+
 		if (sscanf(line, "%x, %x, %x, %x",
 		    &mc->i[count],
 		    &mc->i[count + 1],
@@ -102,6 +117,10 @@
 		unsigned int family, model, stepping;
 		unsigned int year, month, day;
 
+		if ((start > bufsize) ||
+		    ((bufsize - start) < sizeof(struct microcode_header_intel)))
+			goto out;
+
 		mc = (union mcbuf *) &buf[start];
 
 		if (mc->hdr.totalsize)
@@ -109,8 +128,12 @@
 		else
 			size = 2000 + sizeof(struct microcode_header_intel);
 
+		if (size > (bufsize - start))
+			goto out;
+
 		if (mc->hdr.ldrver != 1 || mc->hdr.hdrver != 1) {
-			printf("unknown version/format:\n");
+			printf("unknown version/format: %d/%d\n",
+			       mc->hdr.ldrver, mc->hdr.hdrver);
 			rc = EXIT_FAILURE;
 			break;
 		}
@@ -135,7 +158,11 @@
 		month = mc->hdr.date >> 24;
 		day = (mc->hdr.date >> 16) & 0xff;
 
-		asprintf(&filename, "intel-ucode/%02x-%02x-%02x", family, model, stepping);
+		if (asprintf(&filename, "intel-ucode/%02x-%02x-%02x", family,
+		    model, stepping) == -1) {
+			printf("Failed to generate ucode filename\n");
+			goto out;
+		}
 		printf("\n");
 		printf("%s\n", filename);
 		printf("signature: 0x%02x\n", mc->hdr.sig);
@@ -164,6 +191,11 @@
 	}
 	printf("\n");
 
+	if (start != bufsize)
+		printf("Finished parsing at byte %zu of %zu\n", start, bufsize);
+
  out:
+	free(buf);
+
 	return rc;
 }