[PATCH net] netfilter: nf_conntrack_pptp: prevent buffer overflows in debug code

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* [PATCH net] netfilter: nf_conntrack_pptp: prevent buffer overflows in debug code
@ 2020-05-06 10:17 Dan Carpenter
  2020-05-10 21:46 ` Pablo Neira Ayuso
  0 siblings, 1 reply; 2+ messages in thread
From: Dan Carpenter @ 2020-05-06 10:17 UTC (permalink / raw)
  To: Pablo Neira Ayuso
  Cc: Jozsef Kadlecsik, Florian Westphal, David S. Miller,
	Jakub Kicinski, netfilter-devel, coreteam, netdev,
	kernel-janitors

Smatch complains that the value for "cmd" comes from the network and
can't be trusted.  The value is actually checked at the end of these
functions so I just copied that here as well.

Fixes: f09943fefe6b ("[NETFILTER]: nf_conntrack/nf_nat: add PPTP helper port")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 net/netfilter/nf_conntrack_pptp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_conntrack_pptp.c b/net/netfilter/nf_conntrack_pptp.c
index a971183f11af7..b4dc567f7fb68 100644
--- a/net/netfilter/nf_conntrack_pptp.c
+++ b/net/netfilter/nf_conntrack_pptp.c
@@ -276,7 +276,8 @@ pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 	typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
 
 	msg = ntohs(ctlh->messageType);
-	pr_debug("inbound control message %s\n", pptp_msg_name[msg]);
+	pr_debug("inbound control message %s\n",
+		 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0]);
 
 	switch (msg) {
 	case PPTP_START_SESSION_REPLY:
@@ -404,7 +405,8 @@ pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
 	typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
 
 	msg = ntohs(ctlh->messageType);
-	pr_debug("outbound control message %s\n", pptp_msg_name[msg]);
+	pr_debug("outbound control message %s\n",
+		 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0]);
 
 	switch (msg) {
 	case PPTP_START_SESSION_REQUEST:
-- 
2.26.2


^ permalink raw reply related	[flat|nested] 2+ messages in thread

* Re: [PATCH net] netfilter: nf_conntrack_pptp: prevent buffer overflows in debug code
  2020-05-06 10:17 [PATCH net] netfilter: nf_conntrack_pptp: prevent buffer overflows in debug code Dan Carpenter
@ 2020-05-10 21:46 ` Pablo Neira Ayuso
  0 siblings, 0 replies; 2+ messages in thread
From: Pablo Neira Ayuso @ 2020-05-10 21:46 UTC (permalink / raw)
  To: Dan Carpenter
  Cc: Jozsef Kadlecsik, Florian Westphal, David S. Miller,
	Jakub Kicinski, netfilter-devel, coreteam, netdev,
	kernel-janitors

[-- Attachment #1: Type: text/plain, Size: 542 bytes --]

Hi Dan,

On Wed, May 06, 2020 at 01:17:53PM +0300, Dan Carpenter wrote:
> Smatch complains that the value for "cmd" comes from the network and
> can't be trusted.  The value is actually checked at the end of these
> functions so I just copied that here as well.

I'm attaching another patch, it's based on yours.

It's basically adding a pptp_msg_name() helper function, which is
probably what should have been done in this code since the beginning.

There are many of msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] :
pptp_msg_name[0].

Thank you.

[-- Attachment #2: dan.patch --]
[-- Type: text/x-diff, Size: 6557 bytes --]

commit 8e6a4946266557234412cac3a5adbe88df974dd7
Author: Dan Carpenter <dan.carpenter@oracle.com>
Date:   Wed May 6 13:17:53 2020 +0300

    netfilter: nf_conntrack_pptp: prevent buffer overflows in debug code
    
    Smatch complains that the value for "cmd" comes from the network and
    can't be trusted.
    
    Fixes: f09943fefe6b ("[NETFILTER]: nf_conntrack/nf_nat: add PPTP helper port")
    Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/include/linux/netfilter/nf_conntrack_pptp.h b/include/linux/netfilter/nf_conntrack_pptp.h
index fcc409de31a4..6a4ff6d5ebc2 100644
--- a/include/linux/netfilter/nf_conntrack_pptp.h
+++ b/include/linux/netfilter/nf_conntrack_pptp.h
@@ -10,7 +10,7 @@
 #include <net/netfilter/nf_conntrack_expect.h>
 #include <uapi/linux/netfilter/nf_conntrack_tuple_common.h>
 
-extern const char *const pptp_msg_name[];
+extern const char *const pptp_msg_name(u_int16_t msg);
 
 /* 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 3c25a467b3ef..7afde8828b4c 100644
--- a/net/ipv4/netfilter/nf_nat_pptp.c
+++ b/net/ipv4/netfilter/nf_nat_pptp.c
@@ -166,8 +166,7 @@ pptp_outbound_pkt(struct sk_buff *skb,
 		break;
 	default:
 		pr_debug("unknown outbound packet 0x%04x:%s\n", msg,
-			 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] :
-					       pptp_msg_name[0]);
+			 pptp_msg_name(msg));
 		fallthrough;
 	case PPTP_SET_LINK_INFO:
 		/* only need to NAT in case PAC is behind NAT box */
@@ -268,9 +267,7 @@ pptp_inbound_pkt(struct sk_buff *skb,
 		pcid_off = offsetof(union pptp_ctrl_union, setlink.peersCallID);
 		break;
 	default:
-		pr_debug("unknown inbound packet %s\n",
-			 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] :
-					       pptp_msg_name[0]);
+		pr_debug("unknown inbound packet %s\n", pptp_msg_name(msg));
 		fallthrough;
 	case PPTP_START_SESSION_REQUEST:
 	case PPTP_START_SESSION_REPLY:
diff --git a/net/netfilter/nf_conntrack_pptp.c b/net/netfilter/nf_conntrack_pptp.c
index a971183f11af..512aae5bdb66 100644
--- a/net/netfilter/nf_conntrack_pptp.c
+++ b/net/netfilter/nf_conntrack_pptp.c
@@ -72,7 +72,7 @@ EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
 
 #if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
 /* PptpControlMessageType names */
-const char *const pptp_msg_name[] = {
+static const char *const pptp_msg_name_array[PPTP_MSG_MAX + 1] = {
 	"UNKNOWN_MESSAGE",
 	"START_SESSION_REQUEST",
 	"START_SESSION_REPLY",
@@ -90,6 +90,14 @@ const char *const pptp_msg_name[] = {
 	"WAN_ERROR_NOTIFY",
 	"SET_LINK_INFO"
 };
+
+const char *const pptp_msg_name(u_int16_t msg)
+{
+	if (msg > PPTP_MSG_MAX)
+		return pptp_msg_name_array[0];
+
+	return pptp_msg_name_array[msg];
+}
 EXPORT_SYMBOL(pptp_msg_name);
 #endif
 
@@ -276,7 +284,7 @@ pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 	typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
 
 	msg = ntohs(ctlh->messageType);
-	pr_debug("inbound control message %s\n", pptp_msg_name[msg]);
+	pr_debug("inbound control message %s\n", pptp_msg_name(msg));
 
 	switch (msg) {
 	case PPTP_START_SESSION_REPLY:
@@ -311,7 +319,7 @@ pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 		pcid = pptpReq->ocack.peersCallID;
 		if (info->pns_call_id != pcid)
 			goto invalid;
-		pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg],
+		pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name(msg),
 			 ntohs(cid), ntohs(pcid));
 
 		if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
@@ -328,7 +336,7 @@ pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 			goto invalid;
 
 		cid = pptpReq->icreq.callID;
-		pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
+		pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
 		info->cstate = PPTP_CALL_IN_REQ;
 		info->pac_call_id = cid;
 		break;
@@ -347,7 +355,7 @@ pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 		if (info->pns_call_id != pcid)
 			goto invalid;
 
-		pr_debug("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid));
+		pr_debug("%s, PCID=%X\n", pptp_msg_name(msg), ntohs(pcid));
 		info->cstate = PPTP_CALL_IN_CONF;
 
 		/* we expect a GRE connection from PAC to PNS */
@@ -357,7 +365,7 @@ pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 	case PPTP_CALL_DISCONNECT_NOTIFY:
 		/* server confirms disconnect */
 		cid = pptpReq->disc.callID;
-		pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
+		pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
 		info->cstate = PPTP_CALL_NONE;
 
 		/* untrack this call id, unexpect GRE packets */
@@ -384,7 +392,7 @@ pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 invalid:
 	pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 		 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
-		 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
+		 pptp_msg_name(msg),
 		 msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 		 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 	return NF_ACCEPT;
@@ -404,7 +412,7 @@ pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
 	typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
 
 	msg = ntohs(ctlh->messageType);
-	pr_debug("outbound control message %s\n", pptp_msg_name[msg]);
+	pr_debug("outbound control message %s\n", pptp_msg_name(msg));
 
 	switch (msg) {
 	case PPTP_START_SESSION_REQUEST:
@@ -426,7 +434,7 @@ pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
 		info->cstate = PPTP_CALL_OUT_REQ;
 		/* track PNS call id */
 		cid = pptpReq->ocreq.callID;
-		pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
+		pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
 		info->pns_call_id = cid;
 		break;
 
@@ -440,7 +448,7 @@ pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
 		pcid = pptpReq->icack.peersCallID;
 		if (info->pac_call_id != pcid)
 			goto invalid;
-		pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name[msg],
+		pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name(msg),
 			 ntohs(cid), ntohs(pcid));
 
 		if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
@@ -480,7 +488,7 @@ pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
 invalid:
 	pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 		 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
-		 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
+		 pptp_msg_name(msg),
 		 msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 		 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 	return NF_ACCEPT;

^ permalink raw reply related	[flat|nested] 2+ messages in thread

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2020-05-06 10:17 [PATCH net] netfilter: nf_conntrack_pptp: prevent buffer overflows in debug code Dan Carpenter
2020-05-10 21:46 ` Pablo Neira Ayuso

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