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linux-next/net/ax25/ax25_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

456 lines
10 KiB
C
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/*
* This program 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.
*
* Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
* Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
* Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
* Copyright (C) Hans-Joachim Hetscher DD8NE (dd8ne@bnv-bamberg.de)
*/
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/netfilter.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <asm/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
/*
* Given a fragment, queue it on the fragment queue and if the fragment
* is complete, send it back to ax25_rx_iframe.
*/
static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
{
struct sk_buff *skbn, *skbo;
if (ax25->fragno != 0) {
if (!(*skb->data & AX25_SEG_FIRST)) {
if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
/* Enqueue fragment */
ax25->fragno = *skb->data & AX25_SEG_REM;
skb_pull(skb, 1); /* skip fragno */
ax25->fraglen += skb->len;
skb_queue_tail(&ax25->frag_queue, skb);
/* Last fragment received ? */
if (ax25->fragno == 0) {
skbn = alloc_skb(AX25_MAX_HEADER_LEN +
ax25->fraglen,
GFP_ATOMIC);
if (!skbn) {
skb_queue_purge(&ax25->frag_queue);
return 1;
}
skb_reserve(skbn, AX25_MAX_HEADER_LEN);
skbn->dev = ax25->ax25_dev->dev;
skb_reset_network_header(skbn);
skb_reset_transport_header(skbn);
/* Copy data from the fragments */
while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
skb_copy_from_linear_data(skbo,
skb_put(skbn, skbo->len),
skbo->len);
kfree_skb(skbo);
}
ax25->fraglen = 0;
if (ax25_rx_iframe(ax25, skbn) == 0)
kfree_skb(skbn);
}
return 1;
}
}
} else {
/* First fragment received */
if (*skb->data & AX25_SEG_FIRST) {
skb_queue_purge(&ax25->frag_queue);
ax25->fragno = *skb->data & AX25_SEG_REM;
skb_pull(skb, 1); /* skip fragno */
ax25->fraglen = skb->len;
skb_queue_tail(&ax25->frag_queue, skb);
return 1;
}
}
return 0;
}
/*
* This is where all valid I frames are sent to, to be dispatched to
* whichever protocol requires them.
*/
int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
{
int (*func)(struct sk_buff *, ax25_cb *);
unsigned char pid;
int queued = 0;
if (skb == NULL) return 0;
ax25_start_idletimer(ax25);
pid = *skb->data;
if (pid == AX25_P_IP) {
/* working around a TCP bug to keep additional listeners
* happy. TCP re-uses the buffer and destroys the original
* content.
*/
struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
if (skbn != NULL) {
kfree_skb(skb);
skb = skbn;
}
skb_pull(skb, 1); /* Remove PID */
skb->mac_header = skb->network_header;
skb_reset_network_header(skb);
skb->dev = ax25->ax25_dev->dev;
skb->pkt_type = PACKET_HOST;
skb->protocol = htons(ETH_P_IP);
netif_rx(skb);
return 1;
}
if (pid == AX25_P_SEGMENT) {
skb_pull(skb, 1); /* Remove PID */
return ax25_rx_fragment(ax25, skb);
}
if ((func = ax25_protocol_function(pid)) != NULL) {
skb_pull(skb, 1); /* Remove PID */
return (*func)(skb, ax25);
}
if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
ax25->pidincl) {
if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
queued = 1;
else
ax25->condition |= AX25_COND_OWN_RX_BUSY;
}
}
return queued;
}
/*
* Higher level upcall for a LAPB frame
*/
static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
{
int queued = 0;
if (ax25->state == AX25_STATE_0)
return 0;
switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
case AX25_PROTO_STD_SIMPLEX:
case AX25_PROTO_STD_DUPLEX:
queued = ax25_std_frame_in(ax25, skb, type);
break;
#ifdef CONFIG_AX25_DAMA_SLAVE
case AX25_PROTO_DAMA_SLAVE:
if (dama || ax25->ax25_dev->dama.slave)
queued = ax25_ds_frame_in(ax25, skb, type);
else
queued = ax25_std_frame_in(ax25, skb, type);
break;
#endif
}
return queued;
}
static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
ax25_address *dev_addr, struct packet_type *ptype)
{
ax25_address src, dest, *next_digi = NULL;
int type = 0, mine = 0, dama;
struct sock *make, *sk;
ax25_digi dp, reverse_dp;
ax25_cb *ax25;
ax25_dev *ax25_dev;
/*
* Process the AX.25/LAPB frame.
*/
skb_reset_transport_header(skb);
if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
goto free;
/*
* Parse the address header.
*/
if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL)
goto free;
/*
* Ours perhaps ?
*/
if (dp.lastrepeat + 1 < dp.ndigi) /* Not yet digipeated completely */
next_digi = &dp.calls[dp.lastrepeat + 1];
/*
* Pull of the AX.25 headers leaving the CTRL/PID bytes
*/
skb_pull(skb, ax25_addr_size(&dp));
/* For our port addresses ? */
if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
mine = 1;
/* Also match on any registered callsign from L3/4 */
if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
mine = 1;
/* UI frame - bypass LAPB processing */
if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
skb_set_transport_header(skb, 2); /* skip control and pid */
ax25_send_to_raw(&dest, skb, skb->data[1]);
if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0)
goto free;
/* Now we are pointing at the pid byte */
switch (skb->data[1]) {
case AX25_P_IP:
skb_pull(skb,2); /* drop PID/CTRL */
skb_reset_transport_header(skb);
skb_reset_network_header(skb);
skb->dev = dev;
skb->pkt_type = PACKET_HOST;
skb->protocol = htons(ETH_P_IP);
netif_rx(skb);
break;
case AX25_P_ARP:
skb_pull(skb,2);
skb_reset_transport_header(skb);
skb_reset_network_header(skb);
skb->dev = dev;
skb->pkt_type = PACKET_HOST;
skb->protocol = htons(ETH_P_ARP);
netif_rx(skb);
break;
case AX25_P_TEXT:
/* Now find a suitable dgram socket */
sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
if (sk != NULL) {
bh_lock_sock(sk);
if (atomic_read(&sk->sk_rmem_alloc) >=
sk->sk_rcvbuf) {
kfree_skb(skb);
} else {
/*
* Remove the control and PID.
*/
skb_pull(skb, 2);
if (sock_queue_rcv_skb(sk, skb) != 0)
kfree_skb(skb);
}
bh_unlock_sock(sk);
sock_put(sk);
} else {
kfree_skb(skb);
}
break;
default:
kfree_skb(skb); /* Will scan SOCK_AX25 RAW sockets */
break;
}
return 0;
}
/*
* Is connected mode supported on this device ?
* If not, should we DM the incoming frame (except DMs) or
* silently ignore them. For now we stay quiet.
*/
if (ax25_dev->values[AX25_VALUES_CONMODE] == 0)
goto free;
/* LAPB */
/* AX.25 state 1-4 */
ax25_digi_invert(&dp, &reverse_dp);
if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
/*
* Process the frame. If it is queued up internally it
* returns one otherwise we free it immediately. This
* routine itself wakes the user context layers so we do
* no further work
*/
if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
kfree_skb(skb);
ax25_cb_put(ax25);
return 0;
}
/* AX.25 state 0 (disconnected) */
/* a) received not a SABM(E) */
if ((*skb->data & ~AX25_PF) != AX25_SABM &&
(*skb->data & ~AX25_PF) != AX25_SABME) {
/*
* Never reply to a DM. Also ignore any connects for
* addresses that are not our interfaces and not a socket.
*/
if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
ax25_return_dm(dev, &src, &dest, &dp);
goto free;
}
/* b) received SABM(E) */
if (dp.lastrepeat + 1 == dp.ndigi)
sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
else
sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
if (sk != NULL) {
bh_lock_sock(sk);
if (sk_acceptq_is_full(sk) ||
(make = ax25_make_new(sk, ax25_dev)) == NULL) {
if (mine)
ax25_return_dm(dev, &src, &dest, &dp);
kfree_skb(skb);
bh_unlock_sock(sk);
sock_put(sk);
return 0;
}
ax25 = ax25_sk(make);
skb_set_owner_r(skb, make);
skb_queue_head(&sk->sk_receive_queue, skb);
make->sk_state = TCP_ESTABLISHED;
sk->sk_ack_backlog++;
bh_unlock_sock(sk);
} else {
if (!mine)
goto free;
if ((ax25 = ax25_create_cb()) == NULL) {
ax25_return_dm(dev, &src, &dest, &dp);
goto free;
}
ax25_fillin_cb(ax25, ax25_dev);
}
ax25->source_addr = dest;
ax25->dest_addr = src;
/*
* Sort out any digipeated paths.
*/
if (dp.ndigi && !ax25->digipeat &&
(ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
kfree_skb(skb);
ax25_destroy_socket(ax25);
if (sk)
sock_put(sk);
return 0;
}
if (dp.ndigi == 0) {
kfree(ax25->digipeat);
ax25->digipeat = NULL;
} else {
/* Reverse the source SABM's path */
memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
}
if ((*skb->data & ~AX25_PF) == AX25_SABME) {
ax25->modulus = AX25_EMODULUS;
ax25->window = ax25_dev->values[AX25_VALUES_EWINDOW];
} else {
ax25->modulus = AX25_MODULUS;
ax25->window = ax25_dev->values[AX25_VALUES_WINDOW];
}
ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
#ifdef CONFIG_AX25_DAMA_SLAVE
if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
ax25_dama_on(ax25);
#endif
ax25->state = AX25_STATE_3;
ax25_cb_add(ax25);
ax25_start_heartbeat(ax25);
ax25_start_t3timer(ax25);
ax25_start_idletimer(ax25);
if (sk) {
if (!sock_flag(sk, SOCK_DEAD))
sk->sk_data_ready(sk);
sock_put(sk);
} else {
free:
kfree_skb(skb);
}
return 0;
}
/*
* Receive an AX.25 frame via a SLIP interface.
*/
int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *ptype, struct net_device *orig_dev)
{
skb_orphan(skb);
if (!net_eq(dev_net(dev), &init_net)) {
kfree_skb(skb);
return 0;
}
if ((*skb->data & 0x0F) != 0) {
kfree_skb(skb); /* Not a KISS data frame */
return 0;
}
skb_pull(skb, AX25_KISS_HEADER_LEN); /* Remove the KISS byte */
return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
}
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