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x25: possible skb leak on bad facilities

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Originally x25_parse_facilities returned
-1 for an error
 0 meaning 0 length facilities
>0 the length of the facilities parsed.

5ef41308f9 ("x25: Prevent crashing when parsing bad X.25 facilities") introduced more
error checking in x25_parse_facilities however used 0 to indicate bad parsing
a6331d6f9a ("memory corruption in X.25 facilities parsing") followed this further for
DTE facilities, again using 0 for bad parsing.

The meaning of 0 got confused in the callers.
If the facilities are messed up we can't determine where the data starts.
So patch makes all parsing errors return -1 and ensures callers close and don't use the skb further.

Reported-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Hendry <andrew.hendry@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
andrew hendry 2011-02-07 00:08:15 +00:00 committed by David S. Miller
parent 711c914688
commit 95c3043008
2 changed files with 30 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
net/x25/x25_facilities.c
View File

@ -27,9 +27,19 @@
#include <net/sock.h>
#include <net/x25.h>
/*
* Parse a set of facilities into the facilities structures. Unrecognised
* facilities are written to the debug log file.
/**
* x25_parse_facilities - Parse facilities from skb into the facilities structs
*
* @skb: sk_buff to parse
* @facilities: Regular facilites, updated as facilities are found
* @dte_facs: ITU DTE facilities, updated as DTE facilities are found
* @vc_fac_mask: mask is updated with all facilities found
*
* Return codes:
* -1 - Parsing error, caller should drop call and clean up
* 0 - Parse OK, this skb has no facilities
* >0 - Parse OK, returns the length of the facilities header
*
*/
int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask)
@ -62,7 +72,7 @@ int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
switch (*p & X25_FAC_CLASS_MASK) {
case X25_FAC_CLASS_A:
if (len < 2)
return 0;
return -1;
switch (*p) {
case X25_FAC_REVERSE:
if((p[1] & 0x81) == 0x81) {
@ -107,7 +117,7 @@ int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
break;
case X25_FAC_CLASS_B:
if (len < 3)
return 0;
return -1;
switch (*p) {
case X25_FAC_PACKET_SIZE:
facilities->pacsize_in = p[1];
@ -130,7 +140,7 @@ int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
break;
case X25_FAC_CLASS_C:
if (len < 4)
return 0;
return -1;
printk(KERN_DEBUG "X.25: unknown facility %02X, "
"values %02X, %02X, %02X\n",
p[0], p[1], p[2], p[3]);
@ -139,18 +149,18 @@ int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
break;
case X25_FAC_CLASS_D:
if (len < p[1] + 2)
return 0;
return -1;
switch (*p) {
case X25_FAC_CALLING_AE:
if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
return 0;
return -1;
dte_facs->calling_len = p[2];
memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
*vc_fac_mask |= X25_MASK_CALLING_AE;
break;
case X25_FAC_CALLED_AE:
if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
return 0;
return -1;
dte_facs->called_len = p[2];
memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
*vc_fac_mask |= X25_MASK_CALLED_AE;

14
net/x25/x25_in.c
View File

@ -91,10 +91,10 @@ static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametyp
{
struct x25_address source_addr, dest_addr;
int len;
struct x25_sock *x25 = x25_sk(sk);
switch (frametype) {
case X25_CALL_ACCEPTED: {
struct x25_sock *x25 = x25_sk(sk);
x25_stop_timer(sk);
x25->condition = 0x00;
@ -113,14 +113,16 @@ static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametyp
&dest_addr);
if (len > 0)
skb_pull(skb, len);
else if (len < 0)
goto out_clear;
len = x25_parse_facilities(skb, &x25->facilities,
&x25->dte_facilities,
&x25->vc_facil_mask);
if (len > 0)
skb_pull(skb, len);
else
return -1;
else if (len < 0)
goto out_clear;
/*
* Copy any Call User Data.
*/
@ -144,6 +146,12 @@ static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametyp
}
return 0;
out_clear:
x25_write_internal(sk, X25_CLEAR_REQUEST);
x25->state = X25_STATE_2;
x25_start_t23timer(sk);
return 0;
}
/*