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Commit 95c30430 authored by andrew hendry's avatar andrew hendry Committed by David S. Miller
Browse files

x25: possible skb leak on bad facilities 



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

5ef41308 ("x25: Prevent crashing when parsing bad X.25 facilities") introduced more
error checking in x25_parse_facilities however used 0 to indicate bad parsing
a6331d6f ("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: default avatarAndy Whitcroft <apw@canonical.com>
Signed-off-by: default avatarAndrew Hendry <andrew.hendry@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 711c9146

net/x25/x25_facilities.c

+19 −9
Original line number Diff line number Diff line
@@ -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;

net/x25/x25_in.c

+11 −3
Original line number Diff line number Diff line
@@ -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;

}



/*