Add checks for fgets() when reading proc

If expected proc headers are missing, catch and print error.

ip/ip6tunnel.c

@@ -262,8 +262,11 @@ static int do_tunnels_list(struct ip6_tnl_parm *p)
 	}
 
 	/* skip two lines at the begenning of the file */
-	fgets(buf, sizeof(buf), fp);
-	fgets(buf, sizeof(buf), fp);
+	if (!fgets(buf, sizeof(buf), fp) ||
+	    !fgets(buf, sizeof(buf), fp)) {
+		fprintf(stderr, "/proc/net/dev read error\n");
+		return -1;
+	}
 
 	while (fgets(buf, sizeof(buf), fp) != NULL) {
 		char name[IFNAMSIZ];

ip/ipmaddr.c

@@ -128,7 +128,8 @@ void read_igmp(struct ma_info **result_p)
 	if (!fp)
 		return;
 	memset(&m, 0, sizeof(m));
-	fgets(buf, sizeof(buf), fp);
+	if (!fgets(buf, sizeof(buf), fp))
+		return;
 
 	m.addr.family = AF_INET;
 	m.addr.bitlen = 32;

ip/ipmroute.c

@@ -58,7 +58,8 @@ static void read_viftable(void)
 	if (!fp)
 		return;
 
-	fgets(buf, sizeof(buf), fp);
+	if (!fgets(buf, sizeof(buf), fp))
+		return;
 
 	while (fgets(buf, sizeof(buf), fp)) {
 		int vifi;
@@ -83,7 +84,8 @@ static void read_mroute_list(FILE *ofp)
 	if (!fp)
 		return;
 
-	fgets(buf, sizeof(buf), fp);
+	if (!fgets(buf, sizeof(buf), fp))
+		return;
 
 	while (fgets(buf, sizeof(buf), fp)) {
 		inet_prefix maddr, msrc;

ip/iptunnel.c

@@ -407,8 +407,12 @@ static int do_tunnels_list(struct ip_tunnel_parm *p)
 		return -1;
 	}
 
-	fgets(buf, sizeof(buf), fp);
-	fgets(buf, sizeof(buf), fp);
+	/* skip header lines */
+	if (!fgets(buf, sizeof(buf), fp) ||
+	    !fgets(buf, sizeof(buf), fp)) {
+		fprintf(stderr, "/proc/net/dev read error\n");
+		return -1;
+	}
 
 	while (fgets(buf, sizeof(buf), fp) != NULL) {
 		int index, type;