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Subject[38/44] x25: Patch to fix bug 15678 - x25 accesses fields beyond end of packet.
2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------
From: John Hughes <john@calva.com>

commit f5eb917b861828da18dc28854308068c66d1449a upstream.

Here is a patch to stop X.25 examining fields beyond the end of the packet.

For example, when a simple CALL ACCEPTED was received:

10 10 0f

x25_parse_facilities was attempting to decode the FACILITIES field, but this
packet contains no facilities field.

Signed-off-by: John Hughes <john@calva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
include/net/x25.h | 4 ++++
net/x25/af_x25.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
net/x25/x25_facilities.c | 12 +++++++++++-
net/x25/x25_in.c | 15 +++++++++++----
4 files changed, 72 insertions(+), 6 deletions(-)
--- a/include/net/x25.h
+++ b/include/net/x25.h
@@ -182,6 +182,10 @@ extern int sysctl_x25_clear_request_tim
extern int sysctl_x25_ack_holdback_timeout;
extern int sysctl_x25_forward;

+extern int x25_parse_address_block(struct sk_buff *skb,
+ struct x25_address *called_addr,
+ struct x25_address *calling_addr);
+
extern int x25_addr_ntoa(unsigned char *, struct x25_address *,
struct x25_address *);
extern int x25_addr_aton(unsigned char *, struct x25_address *,
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -80,6 +80,41 @@ struct compat_x25_subscrip_struct {
};
#endif

+
+int x25_parse_address_block(struct sk_buff *skb,
+ struct x25_address *called_addr,
+ struct x25_address *calling_addr)
+{
+ unsigned char len;
+ int needed;
+ int rc;
+
+ if (skb->len < 1) {
+ /* packet has no address block */
+ rc = 0;
+ goto empty;
+ }
+
+ len = *skb->data;
+ needed = 1 + (len >> 4) + (len & 0x0f);
+
+ if (skb->len < needed) {
+ /* packet is too short to hold the addresses it claims
+ to hold */
+ rc = -1;
+ goto empty;
+ }
+
+ return x25_addr_ntoa(skb->data, called_addr, calling_addr);
+
+empty:
+ *called_addr->x25_addr = 0;
+ *calling_addr->x25_addr = 0;
+
+ return rc;
+}
+
+
int x25_addr_ntoa(unsigned char *p, struct x25_address *called_addr,
struct x25_address *calling_addr)
{
@@ -871,16 +906,26 @@ int x25_rx_call_request(struct sk_buff *
/*
* Extract the X.25 addresses and convert them to ASCII strings,
* and remove them.
+ *
+ * Address block is mandatory in call request packets
*/
- addr_len = x25_addr_ntoa(skb->data, &source_addr, &dest_addr);
+ addr_len = x25_parse_address_block(skb, &source_addr, &dest_addr);
+ if (addr_len <= 0)
+ goto out_clear_request;
skb_pull(skb, addr_len);

/*
* Get the length of the facilities, skip past them for the moment
* get the call user data because this is needed to determine
* the correct listener
+ *
+ * Facilities length is mandatory in call request packets
*/
+ if (skb->len < 1)
+ goto out_clear_request;
len = skb->data[0] + 1;
+ if (skb->len < len)
+ goto out_clear_request;
skb_pull(skb,len);

/*
--- a/net/x25/x25_facilities.c
+++ b/net/x25/x25_facilities.c
@@ -35,7 +35,7 @@ int x25_parse_facilities(struct sk_buff
struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask)
{
unsigned char *p = skb->data;
- unsigned int len = *p++;
+ unsigned int len;

*vc_fac_mask = 0;

@@ -50,6 +50,14 @@ int x25_parse_facilities(struct sk_buff
memset(dte_facs->called_ae, '\0', sizeof(dte_facs->called_ae));
memset(dte_facs->calling_ae, '\0', sizeof(dte_facs->calling_ae));

+ if (skb->len < 1)
+ return 0;
+
+ len = *p++;
+
+ if (len >= skb->len)
+ return -1;
+
while (len > 0) {
switch (*p & X25_FAC_CLASS_MASK) {
case X25_FAC_CLASS_A:
@@ -247,6 +255,8 @@ int x25_negotiate_facilities(struct sk_b
memcpy(new, ours, sizeof(*new));

len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
+ if (len < 0)
+ return len;

/*
* They want reverse charging, we won't accept it.
--- a/net/x25/x25_in.c
+++ b/net/x25/x25_in.c
@@ -89,6 +89,7 @@ static int x25_queue_rx_frame(struct soc
static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametype)
{
struct x25_address source_addr, dest_addr;
+ int len;

switch (frametype) {
case X25_CALL_ACCEPTED: {
@@ -106,11 +107,17 @@ static int x25_state1_machine(struct soc
* Parse the data in the frame.
*/
skb_pull(skb, X25_STD_MIN_LEN);
- skb_pull(skb, x25_addr_ntoa(skb->data, &source_addr, &dest_addr));
- skb_pull(skb,
- x25_parse_facilities(skb, &x25->facilities,
+
+ len = x25_parse_address_block(skb, &source_addr,
+ &dest_addr);
+ if (len > 0)
+ skb_pull(skb, len);
+
+ len = x25_parse_facilities(skb, &x25->facilities,
&x25->dte_facilities,
- &x25->vc_facil_mask));
+ &x25->vc_facil_mask);
+ if (len > 0)
+ skb_pull(skb, len);
/*
* Copy any Call User Data.
*/



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