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linux/net/atm/signaling.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

269 lines
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/* net/atm/signaling.c - ATM signaling */
/* Written 1995-2000 by Werner Almesberger, EPFL LRC/ICA */
#define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__
#include <linux/errno.h> /* error codes */
#include <linux/kernel.h> /* printk */
#include <linux/skbuff.h>
#include <linux/wait.h>
#include <linux/sched.h> /* jiffies and HZ */
#include <linux/atm.h> /* ATM stuff */
#include <linux/atmsap.h>
#include <linux/atmsvc.h>
#include <linux/atmdev.h>
#include <linux/bitops.h>
#include <linux/slab.h>
#include "resources.h"
#include "signaling.h"
#undef WAIT_FOR_DEMON /* #define this if system calls on SVC sockets
should block until the demon runs.
Danger: may cause nasty hangs if the demon
crashes. */
struct atm_vcc *sigd = NULL;
#ifdef WAIT_FOR_DEMON
static DECLARE_WAIT_QUEUE_HEAD(sigd_sleep);
#endif
static void sigd_put_skb(struct sk_buff *skb)
{
#ifdef WAIT_FOR_DEMON
DECLARE_WAITQUEUE(wait, current);
add_wait_queue(&sigd_sleep, &wait);
while (!sigd) {
set_current_state(TASK_UNINTERRUPTIBLE);
pr_debug("atmsvc: waiting for signaling daemon...\n");
schedule();
}
current->state = TASK_RUNNING;
remove_wait_queue(&sigd_sleep, &wait);
#else
if (!sigd) {
pr_debug("atmsvc: no signaling daemon\n");
kfree_skb(skb);
return;
}
#endif
atm_force_charge(sigd, skb->truesize);
skb_queue_tail(&sk_atm(sigd)->sk_receive_queue, skb);
sk_atm(sigd)->sk_data_ready(sk_atm(sigd));
}
static void modify_qos(struct atm_vcc *vcc, struct atmsvc_msg *msg)
{
struct sk_buff *skb;
if (test_bit(ATM_VF_RELEASED, &vcc->flags) ||
!test_bit(ATM_VF_READY, &vcc->flags))
return;
msg->type = as_error;
if (!vcc->dev->ops->change_qos)
msg->reply = -EOPNOTSUPP;
else {
/* should lock VCC */
msg->reply = vcc->dev->ops->change_qos(vcc, &msg->qos,
msg->reply);
if (!msg->reply)
msg->type = as_okay;
}
/*
* Should probably just turn around the old skb. But the, the buffer
* space accounting needs to follow the change too. Maybe later.
*/
while (!(skb = alloc_skb(sizeof(struct atmsvc_msg), GFP_KERNEL)))
schedule();
*(struct atmsvc_msg *)skb_put(skb, sizeof(struct atmsvc_msg)) = *msg;
sigd_put_skb(skb);
}
static int sigd_send(struct atm_vcc *vcc, struct sk_buff *skb)
{
struct atmsvc_msg *msg;
struct atm_vcc *session_vcc;
struct sock *sk;
msg = (struct atmsvc_msg *) skb->data;
atomic_sub(skb->truesize, &sk_atm(vcc)->sk_wmem_alloc);
vcc = *(struct atm_vcc **) &msg->vcc;
pr_debug("%d (0x%lx)\n", (int)msg->type, (unsigned long)vcc);
sk = sk_atm(vcc);
switch (msg->type) {
case as_okay:
sk->sk_err = -msg->reply;
clear_bit(ATM_VF_WAITING, &vcc->flags);
if (!*vcc->local.sas_addr.prv && !*vcc->local.sas_addr.pub) {
vcc->local.sas_family = AF_ATMSVC;
memcpy(vcc->local.sas_addr.prv,
msg->local.sas_addr.prv, ATM_ESA_LEN);
memcpy(vcc->local.sas_addr.pub,
msg->local.sas_addr.pub, ATM_E164_LEN + 1);
}
session_vcc = vcc->session ? vcc->session : vcc;
if (session_vcc->vpi || session_vcc->vci)
break;
session_vcc->itf = msg->pvc.sap_addr.itf;
session_vcc->vpi = msg->pvc.sap_addr.vpi;
session_vcc->vci = msg->pvc.sap_addr.vci;
if (session_vcc->vpi || session_vcc->vci)
session_vcc->qos = msg->qos;
break;
case as_error:
clear_bit(ATM_VF_REGIS, &vcc->flags);
clear_bit(ATM_VF_READY, &vcc->flags);
sk->sk_err = -msg->reply;
clear_bit(ATM_VF_WAITING, &vcc->flags);
break;
case as_indicate:
vcc = *(struct atm_vcc **)&msg->listen_vcc;
sk = sk_atm(vcc);
pr_debug("as_indicate!!!\n");
lock_sock(sk);
if (sk_acceptq_is_full(sk)) {
sigd_enq(NULL, as_reject, vcc, NULL, NULL);
dev_kfree_skb(skb);
goto as_indicate_complete;
}
sk->sk_ack_backlog++;
skb_queue_tail(&sk->sk_receive_queue, skb);
pr_debug("waking sk_sleep(sk) 0x%p\n", sk_sleep(sk));
sk->sk_state_change(sk);
as_indicate_complete:
release_sock(sk);
return 0;
case as_close:
set_bit(ATM_VF_RELEASED, &vcc->flags);
vcc_release_async(vcc, msg->reply);
goto out;
case as_modify:
modify_qos(vcc, msg);
break;
case as_addparty:
case as_dropparty:
sk->sk_err_soft = msg->reply;
/* < 0 failure, otherwise ep_ref */
clear_bit(ATM_VF_WAITING, &vcc->flags);
break;
default:
pr_alert("bad message type %d\n", (int)msg->type);
return -EINVAL;
}
sk->sk_state_change(sk);
out:
dev_kfree_skb(skb);
return 0;
}
void sigd_enq2(struct atm_vcc *vcc, enum atmsvc_msg_type type,
struct atm_vcc *listen_vcc, const struct sockaddr_atmpvc *pvc,
const struct sockaddr_atmsvc *svc, const struct atm_qos *qos,
int reply)
{
struct sk_buff *skb;
struct atmsvc_msg *msg;
static unsigned int session = 0;
pr_debug("%d (0x%p)\n", (int)type, vcc);
while (!(skb = alloc_skb(sizeof(struct atmsvc_msg), GFP_KERNEL)))
schedule();
msg = (struct atmsvc_msg *)skb_put(skb, sizeof(struct atmsvc_msg));
memset(msg, 0, sizeof(*msg));
msg->type = type;
*(struct atm_vcc **) &msg->vcc = vcc;
*(struct atm_vcc **) &msg->listen_vcc = listen_vcc;
msg->reply = reply;
if (qos)
msg->qos = *qos;
if (vcc)
msg->sap = vcc->sap;
if (svc)
msg->svc = *svc;
if (vcc)
msg->local = vcc->local;
if (pvc)
msg->pvc = *pvc;
if (vcc) {
if (type == as_connect && test_bit(ATM_VF_SESSION, &vcc->flags))
msg->session = ++session;
/* every new pmp connect gets the next session number */
}
sigd_put_skb(skb);
if (vcc)
set_bit(ATM_VF_REGIS, &vcc->flags);
}
void sigd_enq(struct atm_vcc *vcc, enum atmsvc_msg_type type,
struct atm_vcc *listen_vcc, const struct sockaddr_atmpvc *pvc,
const struct sockaddr_atmsvc *svc)
{
sigd_enq2(vcc, type, listen_vcc, pvc, svc, vcc ? &vcc->qos : NULL, 0);
/* other ISP applications may use "reply" */
}
static void purge_vcc(struct atm_vcc *vcc)
{
if (sk_atm(vcc)->sk_family == PF_ATMSVC &&
!test_bit(ATM_VF_META, &vcc->flags)) {
set_bit(ATM_VF_RELEASED, &vcc->flags);
clear_bit(ATM_VF_REGIS, &vcc->flags);
vcc_release_async(vcc, -EUNATCH);
}
}
static void sigd_close(struct atm_vcc *vcc)
{
struct sock *s;
int i;
pr_debug("\n");
sigd = NULL;
if (skb_peek(&sk_atm(vcc)->sk_receive_queue))
pr_err("closing with requests pending\n");
skb_queue_purge(&sk_atm(vcc)->sk_receive_queue);
read_lock(&vcc_sklist_lock);
for (i = 0; i < VCC_HTABLE_SIZE; ++i) {
struct hlist_head *head = &vcc_hash[i];
sk_for_each(s, head) {
vcc = atm_sk(s);
purge_vcc(vcc);
}
}
read_unlock(&vcc_sklist_lock);
}
static struct atmdev_ops sigd_dev_ops = {
.close = sigd_close,
.send = sigd_send
};
static struct atm_dev sigd_dev = {
.ops = &sigd_dev_ops,
.type = "sig",
.number = 999,
.lock = __SPIN_LOCK_UNLOCKED(sigd_dev.lock)
};
int sigd_attach(struct atm_vcc *vcc)
{
if (sigd)
return -EADDRINUSE;
pr_debug("\n");
sigd = vcc;
vcc->dev = &sigd_dev;
vcc_insert_socket(sk_atm(vcc));
set_bit(ATM_VF_META, &vcc->flags);
set_bit(ATM_VF_READY, &vcc->flags);
#ifdef WAIT_FOR_DEMON
wake_up(&sigd_sleep);
#endif
return 0;
}
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