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Subject[PATCH 4.9 52/61] netfilter: nf_conntrack_pptp: prevent buffer overflows in debug code
Date
From: Pablo Neira Ayuso <pablo@netfilter.org>

commit 4c559f15efcc43b996f4da528cd7f9483aaca36d upstream.

Dan Carpenter says: "Smatch complains that the value for "cmd" comes
from the network and can't be trusted."

Add pptp_msg_name() helper function that checks for the array boundary.

Fixes: f09943fefe6b ("[NETFILTER]: nf_conntrack/nf_nat: add PPTP helper port")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/linux/netfilter/nf_conntrack_pptp.h | 2
net/ipv4/netfilter/nf_nat_pptp.c | 7 ---
net/netfilter/nf_conntrack_pptp.c | 62 +++++++++++++++-------------
3 files changed, 38 insertions(+), 33 deletions(-)

--- 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 *const pptp_msg_name[];
+extern const char *const pptp_msg_name(u_int16_t msg);

/* state of the control session */
enum pptp_ctrlsess_state {
--- a/net/ipv4/netfilter/nf_nat_pptp.c
+++ b/net/ipv4/netfilter/nf_nat_pptp.c
@@ -156,8 +156,7 @@ 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));
/* fall through */
case PPTP_SET_LINK_INFO:
/* only need to NAT in case PAC is behind NAT box */
@@ -250,9 +249,7 @@ 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));
/* fall through */
case PPTP_START_SESSION_REQUEST:
case PPTP_START_SESSION_REPLY:
--- a/net/netfilter/nf_conntrack_pptp.c
+++ b/net/netfilter/nf_conntrack_pptp.c
@@ -71,24 +71,32 @@ EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expec

#if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
/* PptpControlMessageType names */
-const char *const pptp_msg_name[] = {
- "UNKNOWN_MESSAGE",
- "START_SESSION_REQUEST",
- "START_SESSION_REPLY",
- "STOP_SESSION_REQUEST",
- "STOP_SESSION_REPLY",
- "ECHO_REQUEST",
- "ECHO_REPLY",
- "OUT_CALL_REQUEST",
- "OUT_CALL_REPLY",
- "IN_CALL_REQUEST",
- "IN_CALL_REPLY",
- "IN_CALL_CONNECT",
- "CALL_CLEAR_REQUEST",
- "CALL_DISCONNECT_NOTIFY",
- "WAN_ERROR_NOTIFY",
- "SET_LINK_INFO"
+static const char *const pptp_msg_name_array[PPTP_MSG_MAX + 1] = {
+ [0] = "UNKNOWN_MESSAGE",
+ [PPTP_START_SESSION_REQUEST] = "START_SESSION_REQUEST",
+ [PPTP_START_SESSION_REPLY] = "START_SESSION_REPLY",
+ [PPTP_STOP_SESSION_REQUEST] = "STOP_SESSION_REQUEST",
+ [PPTP_STOP_SESSION_REPLY] = "STOP_SESSION_REPLY",
+ [PPTP_ECHO_REQUEST] = "ECHO_REQUEST",
+ [PPTP_ECHO_REPLY] = "ECHO_REPLY",
+ [PPTP_OUT_CALL_REQUEST] = "OUT_CALL_REQUEST",
+ [PPTP_OUT_CALL_REPLY] = "OUT_CALL_REPLY",
+ [PPTP_IN_CALL_REQUEST] = "IN_CALL_REQUEST",
+ [PPTP_IN_CALL_REPLY] = "IN_CALL_REPLY",
+ [PPTP_IN_CALL_CONNECT] = "IN_CALL_CONNECT",
+ [PPTP_CALL_CLEAR_REQUEST] = "CALL_CLEAR_REQUEST",
+ [PPTP_CALL_DISCONNECT_NOTIFY] = "CALL_DISCONNECT_NOTIFY",
+ [PPTP_WAN_ERROR_NOTIFY] = "WAN_ERROR_NOTIFY",
+ [PPTP_SET_LINK_INFO] = "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

@@ -277,7 +285,7 @@ pptp_inbound_pkt(struct sk_buff *skb, un
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:
@@ -312,7 +320,7 @@ pptp_inbound_pkt(struct sk_buff *skb, un
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) {
@@ -329,7 +337,7 @@ pptp_inbound_pkt(struct sk_buff *skb, un
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;
@@ -348,7 +356,7 @@ pptp_inbound_pkt(struct sk_buff *skb, un
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 */
@@ -358,7 +366,7 @@ pptp_inbound_pkt(struct sk_buff *skb, un
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 */
@@ -385,7 +393,7 @@ pptp_inbound_pkt(struct sk_buff *skb, un
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;
@@ -405,7 +413,7 @@ pptp_outbound_pkt(struct sk_buff *skb, u
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:
@@ -427,7 +435,7 @@ pptp_outbound_pkt(struct sk_buff *skb, u
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;

@@ -441,7 +449,7 @@ pptp_outbound_pkt(struct sk_buff *skb, u
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) {
@@ -481,7 +489,7 @@ pptp_outbound_pkt(struct sk_buff *skb, u
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;

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