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linux/net/x25/x25_in.c
David S. Miller 676d23690f net: Fix use after free by removing length arg from sk_data_ready callbacks. 
Several spots in the kernel perform a sequence like:

	skb_queue_tail(&sk->s_receive_queue, skb);
	sk->sk_data_ready(sk, skb->len);

But at the moment we place the SKB onto the socket receive queue it
can be consumed and freed up.  So this skb->len access is potentially
to freed up memory.

Furthermore, the skb->len can be modified by the consumer so it is
possible that the value isn't accurate.

And finally, no actual implementation of this callback actually uses
the length argument.  And since nobody actually cared about it's
value, lots of call sites pass arbitrary values in such as '0' and
even '1'.

So just remove the length argument from the callback, that way there
is no confusion whatsoever and all of these use-after-free cases get
fixed as a side effect.

Based upon a patch by Eric Dumazet and his suggestion to audit this
issue tree-wide.

Signed-off-by: David S. Miller <davem@davemloft.net>
2014-04-11 16:15:36 -04:00

420 lines
9.8 KiB
C
Raw Blame History

/*
* X.25 Packet Layer release 002
*
* This is ALPHA test software. This code may break your machine,
* randomly fail to work with new releases, misbehave and/or generally
* screw up. It might even work.
*
* This code REQUIRES 2.1.15 or higher
*
* This module:
* This module is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* History
* X.25 001 Jonathan Naylor Started coding.
* X.25 002 Jonathan Naylor Centralised disconnection code.
* New timer architecture.
* 2000-03-20 Daniela Squassoni Disabling/enabling of facilities
* negotiation.
* 2000-11-10 Henner Eisen Check and reset for out-of-sequence
* i-frames.
*/
#define pr_fmt(fmt) "X25: " fmt
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <net/x25.h>
static int x25_queue_rx_frame(struct sock *sk, struct sk_buff *skb, int more)
{
struct sk_buff *skbo, *skbn = skb;
struct x25_sock *x25 = x25_sk(sk);
if (more) {
x25->fraglen += skb->len;
skb_queue_tail(&x25->fragment_queue, skb);
skb_set_owner_r(skb, sk);
return 0;
}
if (!more && x25->fraglen > 0) { /* End of fragment */
int len = x25->fraglen + skb->len;
if ((skbn = alloc_skb(len, GFP_ATOMIC)) == NULL){
kfree_skb(skb);
return 1;
}
skb_queue_tail(&x25->fragment_queue, skb);
skb_reset_transport_header(skbn);
skbo = skb_dequeue(&x25->fragment_queue);
skb_copy_from_linear_data(skbo, skb_put(skbn, skbo->len),
skbo->len);
kfree_skb(skbo);
while ((skbo =
skb_dequeue(&x25->fragment_queue)) != NULL) {
skb_pull(skbo, (x25->neighbour->extended) ?
X25_EXT_MIN_LEN : X25_STD_MIN_LEN);
skb_copy_from_linear_data(skbo,
skb_put(skbn, skbo->len),
skbo->len);
kfree_skb(skbo);
}
x25->fraglen = 0;
}
skb_set_owner_r(skbn, sk);
skb_queue_tail(&sk->sk_receive_queue, skbn);
if (!sock_flag(sk, SOCK_DEAD))
sk->sk_data_ready(sk);
return 0;
}
/*
* State machine for state 1, Awaiting Call Accepted State.
* The handling of the timer(s) is in file x25_timer.c.
* Handling of state 0 and connection release is in af_x25.c.
*/
static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametype)
{
struct x25_address source_addr, dest_addr;
int len;
struct x25_sock *x25 = x25_sk(sk);
switch (frametype) {
case X25_CALL_ACCEPTED: {
x25_stop_timer(sk);
x25->condition = 0x00;
x25->vs = 0;
x25->va = 0;
x25->vr = 0;
x25->vl = 0;
x25->state = X25_STATE_3;
sk->sk_state = TCP_ESTABLISHED;
/*
* Parse the data in the frame.
*/
if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
goto out_clear;
skb_pull(skb, X25_STD_MIN_LEN);
len = x25_parse_address_block(skb, &source_addr,
&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 if (len < 0)
goto out_clear;
/*
* Copy any Call User Data.
*/
if (skb->len > 0) {
if (skb->len > X25_MAX_CUD_LEN)
goto out_clear;
skb_copy_bits(skb, 0, x25->calluserdata.cuddata,
skb->len);
x25->calluserdata.cudlength = skb->len;
}
if (!sock_flag(sk, SOCK_DEAD))
sk->sk_state_change(sk);
break;
}
case X25_CLEAR_REQUEST:
if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
goto out_clear;
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]);
break;
default:
break;
}
return 0;
out_clear:
x25_write_internal(sk, X25_CLEAR_REQUEST);
x25->state = X25_STATE_2;
x25_start_t23timer(sk);
return 0;
}
/*
* State machine for state 2, Awaiting Clear Confirmation State.
* The handling of the timer(s) is in file x25_timer.c
* Handling of state 0 and connection release is in af_x25.c.
*/
static int x25_state2_machine(struct sock *sk, struct sk_buff *skb, int frametype)
{
switch (frametype) {
case X25_CLEAR_REQUEST:
if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
goto out_clear;
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
break;
case X25_CLEAR_CONFIRMATION:
x25_disconnect(sk, 0, 0, 0);
break;
default:
break;
}
return 0;
out_clear:
x25_write_internal(sk, X25_CLEAR_REQUEST);
x25_start_t23timer(sk);
return 0;
}
/*
* State machine for state 3, Connected State.
* The handling of the timer(s) is in file x25_timer.c
* Handling of state 0 and connection release is in af_x25.c.
*/
static int x25_state3_machine(struct sock *sk, struct sk_buff *skb, int frametype, int ns, int nr, int q, int d, int m)
{
int queued = 0;
int modulus;
struct x25_sock *x25 = x25_sk(sk);
modulus = (x25->neighbour->extended) ? X25_EMODULUS : X25_SMODULUS;
switch (frametype) {
case X25_RESET_REQUEST:
x25_write_internal(sk, X25_RESET_CONFIRMATION);
x25_stop_timer(sk);
x25->condition = 0x00;
x25->vs = 0;
x25->vr = 0;
x25->va = 0;
x25->vl = 0;
x25_requeue_frames(sk);
break;
case X25_CLEAR_REQUEST:
if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
goto out_clear;
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
break;
case X25_RR:
case X25_RNR:
if (!x25_validate_nr(sk, nr)) {
x25_clear_queues(sk);
x25_write_internal(sk, X25_RESET_REQUEST);
x25_start_t22timer(sk);
x25->condition = 0x00;
x25->vs = 0;
x25->vr = 0;
x25->va = 0;
x25->vl = 0;
x25->state = X25_STATE_4;
} else {
x25_frames_acked(sk, nr);
if (frametype == X25_RNR) {
x25->condition |= X25_COND_PEER_RX_BUSY;
} else {
x25->condition &= ~X25_COND_PEER_RX_BUSY;
}
}
break;
case X25_DATA: /* XXX */
x25->condition &= ~X25_COND_PEER_RX_BUSY;
if ((ns != x25->vr) || !x25_validate_nr(sk, nr)) {
x25_clear_queues(sk);
x25_write_internal(sk, X25_RESET_REQUEST);
x25_start_t22timer(sk);
x25->condition = 0x00;
x25->vs = 0;
x25->vr = 0;
x25->va = 0;
x25->vl = 0;
x25->state = X25_STATE_4;
break;
}
x25_frames_acked(sk, nr);
if (ns == x25->vr) {
if (x25_queue_rx_frame(sk, skb, m) == 0) {
x25->vr = (x25->vr + 1) % modulus;
queued = 1;
} else {
/* Should never happen */
x25_clear_queues(sk);
x25_write_internal(sk, X25_RESET_REQUEST);
x25_start_t22timer(sk);
x25->condition = 0x00;
x25->vs = 0;
x25->vr = 0;
x25->va = 0;
x25->vl = 0;
x25->state = X25_STATE_4;
break;
}
if (atomic_read(&sk->sk_rmem_alloc) >
(sk->sk_rcvbuf >> 1))
x25->condition |= X25_COND_OWN_RX_BUSY;
}
/*
* If the window is full Ack it immediately, else
* start the holdback timer.
*/
if (((x25->vl + x25->facilities.winsize_in) % modulus) == x25->vr) {
x25->condition &= ~X25_COND_ACK_PENDING;
x25_stop_timer(sk);
x25_enquiry_response(sk);
} else {
x25->condition |= X25_COND_ACK_PENDING;
x25_start_t2timer(sk);
}
break;
case X25_INTERRUPT_CONFIRMATION:
clear_bit(X25_INTERRUPT_FLAG, &x25->flags);
break;
case X25_INTERRUPT:
if (sock_flag(sk, SOCK_URGINLINE))
queued = !sock_queue_rcv_skb(sk, skb);
else {
skb_set_owner_r(skb, sk);
skb_queue_tail(&x25->interrupt_in_queue, skb);
queued = 1;
}
sk_send_sigurg(sk);
x25_write_internal(sk, X25_INTERRUPT_CONFIRMATION);
break;
default:
pr_warn("unknown %02X in state 3\n", frametype);
break;
}
return queued;
out_clear:
x25_write_internal(sk, X25_CLEAR_REQUEST);
x25->state = X25_STATE_2;
x25_start_t23timer(sk);
return 0;
}
/*
* State machine for state 4, Awaiting Reset Confirmation State.
* The handling of the timer(s) is in file x25_timer.c
* Handling of state 0 and connection release is in af_x25.c.
*/
static int x25_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype)
{
struct x25_sock *x25 = x25_sk(sk);
switch (frametype) {
case X25_RESET_REQUEST:
x25_write_internal(sk, X25_RESET_CONFIRMATION);
case X25_RESET_CONFIRMATION: {
x25_stop_timer(sk);
x25->condition = 0x00;
x25->va = 0;
x25->vr = 0;
x25->vs = 0;
x25->vl = 0;
x25->state = X25_STATE_3;
x25_requeue_frames(sk);
break;
}
case X25_CLEAR_REQUEST:
if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
goto out_clear;
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
break;
default:
break;
}
return 0;
out_clear:
x25_write_internal(sk, X25_CLEAR_REQUEST);
x25->state = X25_STATE_2;
x25_start_t23timer(sk);
return 0;
}
/* Higher level upcall for a LAPB frame */
int x25_process_rx_frame(struct sock *sk, struct sk_buff *skb)
{
struct x25_sock *x25 = x25_sk(sk);
int queued = 0, frametype, ns, nr, q, d, m;
if (x25->state == X25_STATE_0)
return 0;
frametype = x25_decode(sk, skb, &ns, &nr, &q, &d, &m);
switch (x25->state) {
case X25_STATE_1:
queued = x25_state1_machine(sk, skb, frametype);
break;
case X25_STATE_2:
queued = x25_state2_machine(sk, skb, frametype);
break;
case X25_STATE_3:
queued = x25_state3_machine(sk, skb, frametype, ns, nr, q, d, m);
break;
case X25_STATE_4:
queued = x25_state4_machine(sk, skb, frametype);
break;
}
x25_kick(sk);
return queued;
}
int x25_backlog_rcv(struct sock *sk, struct sk_buff *skb)
{
int queued = x25_process_rx_frame(sk, skb);
if (!queued)
kfree_skb(skb);
return 0;
}
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