diff --git a/include/linux/netfilter/nf_conntrack_pptp.h b/include/linux/netfilter/nf_conntrack_pptp.h
index 23435496d24a..3bbde0c3a8a6 100644
--- a/include/linux/netfilter/nf_conntrack_pptp.h
+++ b/include/linux/netfilter/nf_conntrack_pptp.h
@@ -4,7 +4,7 @@
 
 #include <linux/netfilter/nf_conntrack_common.h>
 
-extern const char *pptp_msg_name[];
+extern const char *const pptp_msg_name[];
 
 /* state of the control session */
 enum pptp_ctrlsess_state {
diff --git a/net/ipv4/netfilter/nf_nat_pptp.c b/net/ipv4/netfilter/nf_nat_pptp.c
index e63b944a2ebb..3a1e6d6afc0a 100644
--- a/net/ipv4/netfilter/nf_nat_pptp.c
+++ b/net/ipv4/netfilter/nf_nat_pptp.c
@@ -40,11 +40,11 @@ MODULE_ALIAS("ip_nat_pptp");
 static void pptp_nat_expected(struct nf_conn *ct,
 			      struct nf_conntrack_expect *exp)
 {
-	struct nf_conn *master = ct->master;
+	const struct nf_conn *master = ct->master;
 	struct nf_conntrack_expect *other_exp;
 	struct nf_conntrack_tuple t;
-	struct nf_ct_pptp_master *ct_pptp_info;
-	struct nf_nat_pptp *nat_pptp_info;
+	const struct nf_ct_pptp_master *ct_pptp_info;
+	const struct nf_nat_pptp *nat_pptp_info;
 	struct nf_nat_range range;
 
 	ct_pptp_info = &nfct_help(master)->help.ct_pptp_info;
@@ -186,7 +186,7 @@ static void
 pptp_exp_gre(struct nf_conntrack_expect *expect_orig,
 	     struct nf_conntrack_expect *expect_reply)
 {
-	struct nf_conn *ct = expect_orig->master;
+	const struct nf_conn *ct = expect_orig->master;
 	struct nf_ct_pptp_master *ct_pptp_info;
 	struct nf_nat_pptp *nat_pptp_info;
 
@@ -217,7 +217,7 @@ pptp_inbound_pkt(struct sk_buff *skb,
 		 struct PptpControlHeader *ctlh,
 		 union pptp_ctrl_union *pptpReq)
 {
-	struct nf_nat_pptp *nat_pptp_info;
+	const struct nf_nat_pptp *nat_pptp_info;
 	u_int16_t msg;
 	__be16 new_pcid;
 	unsigned int pcid_off;
diff --git a/net/netfilter/nf_conntrack_pptp.c b/net/netfilter/nf_conntrack_pptp.c
index 099b6df3e2b5..b5cb8e831230 100644
--- a/net/netfilter/nf_conntrack_pptp.c
+++ b/net/netfilter/nf_conntrack_pptp.c
@@ -67,7 +67,7 @@ EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
 
 #ifdef DEBUG
 /* PptpControlMessageType names */
-const char *pptp_msg_name[] = {
+const char *const pptp_msg_name[] = {
 	"UNKNOWN_MESSAGE",
 	"START_SESSION_REQUEST",
 	"START_SESSION_REPLY",
@@ -136,7 +136,7 @@ static void pptp_expectfn(struct nf_conn *ct,
 
 static int destroy_sibling_or_exp(const struct nf_conntrack_tuple *t)
 {
-	struct nf_conntrack_tuple_hash *h;
+	const struct nf_conntrack_tuple_hash *h;
 	struct nf_conntrack_expect *exp;
 	struct nf_conn *sibling;
 
@@ -168,7 +168,7 @@ static int destroy_sibling_or_exp(const struct nf_conntrack_tuple *t)
 /* timeout GRE data connections */
 static void pptp_destroy_siblings(struct nf_conn *ct)
 {
-	struct nf_conn_help *help = nfct_help(ct);
+	const struct nf_conn_help *help = nfct_help(ct);
 	struct nf_conntrack_tuple t;
 
 	nf_ct_gre_keymap_destroy(ct);
@@ -497,9 +497,11 @@ conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
 
 {
 	int dir = CTINFO2DIR(ctinfo);
-	struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
-	struct tcphdr _tcph, *tcph;
-	struct pptp_pkt_hdr _pptph, *pptph;
+	const struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
+	const struct tcphdr *tcph;
+	struct tcphdr _tcph;
+	const struct pptp_pkt_hdr *pptph;
+	struct pptp_pkt_hdr _pptph;
 	struct PptpControlHeader _ctlh, *ctlh;
 	union pptp_ctrl_union _pptpReq, *pptpReq;
 	unsigned int tcplen = skb->len - protoff;