[ Upstream commit 7d8a3a477b3e25ada8dc71d22048c2ea417209a0 ]
There are session cleanup problems in ax25_release() and
ax25_disconnect(). If we setup a session and then disconnect,
the disconnected session is still in "LISTENING" state that
is shown below.
Active AX.25 sockets
Dest Source Device State Vr/Vs Send-Q Recv-Q
DL9SAU-4 DL9SAU-3 ??? LISTENING 000/000 0 0
DL9SAU-3 DL9SAU-4 ??? LISTENING 000/000 0 0
The first reason is caused by del_timer_sync() in ax25_release().
The timers of ax25 are used for correct session cleanup. If we use
ax25_release() to close ax25 sessions and ax25_dev is not null,
the del_timer_sync() functions in ax25_release() will execute.
As a result, the sessions could not be cleaned up correctly,
because the timers have stopped.
In order to solve this problem, this patch adds a device_up flag
in ax25_dev in order to judge whether the device is up. If there
are sessions to be cleaned up, the del_timer_sync() in
ax25_release() will not execute. What's more, we add ax25_cb_del()
in ax25_kill_by_device(), because the timers have been stopped
and there are no functions that could delete ax25_cb if we do not
call ax25_release(). Finally, we reorder the position of
ax25_list_lock in ax25_cb_del() in order to synchronize among
different functions that call ax25_cb_del().
The second reason is caused by improper check in ax25_disconnect().
The incoming ax25 sessions which ax25->sk is null will close
heartbeat timer, because the check "if(!ax25->sk || ..)" is
satisfied. As a result, the session could not be cleaned up properly.
In order to solve this problem, this patch changes the improper
check to "if(ax25->sk && ..)" in ax25_disconnect().
What`s more, the ax25_disconnect() may be called twice, which is
not necessary. For example, ax25_kill_by_device() calls
ax25_disconnect() and sets ax25->state to AX25_STATE_0, but
ax25_release() calls ax25_disconnect() again.
In order to solve this problem, this patch add a check in
ax25_release(). If the flag of ax25->sk equals to SOCK_DEAD,
the ax25_disconnect() in ax25_release() should not be executed.
Fixes: 82e31755e55f ("ax25: Fix UAF bugs in ax25 timers")
Fixes: 8a367e74c012 ("ax25: Fix segfault after sock connection timeout")
Reported-and-tested-by: Thomas Osterried <thomas@osterried.de>
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://lore.kernel.org/r/20220530152158.108619-1-duoming@zju.edu.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 82e31755e55fbcea6a9dfaae5fe4860ade17cbc0 upstream.
There are race conditions that may lead to UAF bugs in
ax25_heartbeat_expiry(), ax25_t1timer_expiry(), ax25_t2timer_expiry(),
ax25_t3timer_expiry() and ax25_idletimer_expiry(), when we call
ax25_release() to deallocate ax25_dev.
One of the UAF bugs caused by ax25_release() is shown below:
(Thread 1) | (Thread 2)
ax25_dev_device_up() //(1) |
... | ax25_kill_by_device()
ax25_bind() //(2) |
ax25_connect() | ...
ax25_std_establish_data_link() |
ax25_start_t1timer() | ax25_dev_device_down() //(3)
mod_timer(&ax25->t1timer,..) |
| ax25_release()
(wait a time) | ...
| ax25_dev_put(ax25_dev) //(4)FREE
ax25_t1timer_expiry() |
ax25->ax25_dev->values[..] //USE| ...
... |
We increase the refcount of ax25_dev in position (1) and (2), and
decrease the refcount of ax25_dev in position (3) and (4).
The ax25_dev will be freed in position (4) and be used in
ax25_t1timer_expiry().
The fail log is shown below:
==============================================================
[ 106.116942] BUG: KASAN: use-after-free in ax25_t1timer_expiry+0x1c/0x60
[ 106.116942] Read of size 8 at addr ffff88800bda9028 by task swapper/0/0
[ 106.116942] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.17.0-06123-g0905eec574
[ 106.116942] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-14
[ 106.116942] Call Trace:
...
[ 106.116942] ax25_t1timer_expiry+0x1c/0x60
[ 106.116942] call_timer_fn+0x122/0x3d0
[ 106.116942] __run_timers.part.0+0x3f6/0x520
[ 106.116942] run_timer_softirq+0x4f/0xb0
[ 106.116942] __do_softirq+0x1c2/0x651
...
This patch adds del_timer_sync() in ax25_release(), which could ensure
that all timers stop before we deallocate ax25_dev.
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 5352a761308397a0e6250fdc629bb3f615b94747 upstream.
There are UAF bugs in ax25_send_control(), when we call ax25_release()
to deallocate ax25_dev. The possible race condition is shown below:
(Thread 1) | (Thread 2)
ax25_dev_device_up() //(1) |
| ax25_kill_by_device()
ax25_bind() //(2) |
ax25_connect() | ...
ax25->state = AX25_STATE_1 |
... | ax25_dev_device_down() //(3)
(Thread 3)
ax25_release() |
ax25_dev_put() //(4) FREE |
case AX25_STATE_1: |
ax25_send_control() |
alloc_skb() //USE |
The refcount of ax25_dev increases in position (1) and (2), and
decreases in position (3) and (4). The ax25_dev will be freed
before dereference sites in ax25_send_control().
The following is part of the report:
[ 102.297448] BUG: KASAN: use-after-free in ax25_send_control+0x33/0x210
[ 102.297448] Read of size 8 at addr ffff888009e6e408 by task ax25_close/602
[ 102.297448] Call Trace:
[ 102.303751] ax25_send_control+0x33/0x210
[ 102.303751] ax25_release+0x356/0x450
[ 102.305431] __sock_release+0x6d/0x120
[ 102.305431] sock_close+0xf/0x20
[ 102.305431] __fput+0x11f/0x420
[ 102.305431] task_work_run+0x86/0xd0
[ 102.307130] get_signal+0x1075/0x1220
[ 102.308253] arch_do_signal_or_restart+0x1df/0xc00
[ 102.308253] exit_to_user_mode_prepare+0x150/0x1e0
[ 102.308253] syscall_exit_to_user_mode+0x19/0x50
[ 102.308253] do_syscall_64+0x48/0x90
[ 102.308253] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 102.308253] RIP: 0033:0x405ae7
This patch defers the free operation of ax25_dev and net_device after
all corresponding dereference sites in ax25_release() to avoid UAF.
Fixes: 9fd75b66b8f6 ("ax25: Fix refcount leaks caused by ax25_cb_del()")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit fc6d01ff9ef03b66d4a3a23b46fc3c3d8cf92009 ]
The previous commit 7ec02f5ac8a5 ("ax25: fix NPD bug in ax25_disconnect")
move ax25_disconnect into lock_sock() in order to prevent NPD bugs. But
there are race conditions that may lead to null pointer dereferences in
ax25_heartbeat_expiry(), ax25_t1timer_expiry(), ax25_t2timer_expiry(),
ax25_t3timer_expiry() and ax25_idletimer_expiry(), when we use
ax25_kill_by_device() to detach the ax25 device.
One of the race conditions that cause null pointer dereferences can be
shown as below:
(Thread 1) | (Thread 2)
ax25_connect() |
ax25_std_establish_data_link() |
ax25_start_t1timer() |
mod_timer(&ax25->t1timer,..) |
| ax25_kill_by_device()
(wait a time) | ...
| s->ax25_dev = NULL; //(1)
ax25_t1timer_expiry() |
ax25->ax25_dev->values[..] //(2)| ...
... |
We set null to ax25_cb->ax25_dev in position (1) and dereference
the null pointer in position (2).
The corresponding fail log is shown below:
===============================================================
BUG: kernel NULL pointer dereference, address: 0000000000000050
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.17.0-rc6-00794-g45690b7d0
RIP: 0010:ax25_t1timer_expiry+0x12/0x40
...
Call Trace:
call_timer_fn+0x21/0x120
__run_timers.part.0+0x1ca/0x250
run_timer_softirq+0x2c/0x60
__do_softirq+0xef/0x2f3
irq_exit_rcu+0xb6/0x100
sysvec_apic_timer_interrupt+0xa2/0xd0
...
This patch moves ax25_disconnect() before s->ax25_dev = NULL
and uses del_timer_sync() to delete timers in ax25_disconnect().
If ax25_disconnect() is called by ax25_kill_by_device() or
ax25->ax25_dev is NULL, the reason in ax25_disconnect() will be
equal to ENETUNREACH, it will wait all timers to stop before we
set null to s->ax25_dev in ax25_kill_by_device().
Fixes: 7ec02f5ac8a5 ("ax25: fix NPD bug in ax25_disconnect")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 9fd75b66b8f68498454d685dc4ba13192ae069b0 ]
The previous commit d01ffb9eee4a ("ax25: add refcount in ax25_dev to
avoid UAF bugs") and commit feef318c855a ("ax25: fix UAF bugs of
net_device caused by rebinding operation") increase the refcounts of
ax25_dev and net_device in ax25_bind() and decrease the matching refcounts
in ax25_kill_by_device() in order to prevent UAF bugs, but there are
reference count leaks.
The root cause of refcount leaks is shown below:
(Thread 1) | (Thread 2)
ax25_bind() |
... |
ax25_addr_ax25dev() |
ax25_dev_hold() //(1) |
... |
dev_hold_track() //(2) |
... | ax25_destroy_socket()
| ax25_cb_del()
| ...
| hlist_del_init() //(3)
|
|
(Thread 3) |
ax25_kill_by_device() |
... |
ax25_for_each(s, &ax25_list) { |
if (s->ax25_dev == ax25_dev) //(4) |
... |
Firstly, we use ax25_bind() to increase the refcount of ax25_dev in
position (1) and increase the refcount of net_device in position (2).
Then, we use ax25_cb_del() invoked by ax25_destroy_socket() to delete
ax25_cb in hlist in position (3) before calling ax25_kill_by_device().
Finally, the decrements of refcounts in ax25_kill_by_device() will not
be executed, because no s->ax25_dev equals to ax25_dev in position (4).
This patch adds decrements of refcounts in ax25_release() and use
lock_sock() to do synchronization. If refcounts decrease in ax25_release(),
the decrements of refcounts in ax25_kill_by_device() will not be
executed and vice versa.
Fixes: d01ffb9eee4a ("ax25: add refcount in ax25_dev to avoid UAF bugs")
Fixes: 87563a043cef ("ax25: fix reference count leaks of ax25_dev")
Fixes: feef318c855a ("ax25: fix UAF bugs of net_device caused by rebinding operation")
Reported-by: Thomas Osterried <thomas@osterried.de>
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
When two ax25 devices attempted to establish connection, the requester use ax25_create(),
ax25_bind() and ax25_connect() to initiate connection. The receiver use ax25_rcv() to
accept connection and use ax25_create_cb() in ax25_rcv() to create ax25_cb, but the
ax25_cb->sk is NULL. When the receiver is detaching, a NULL pointer dereference bug
caused by sock_hold(sk) in ax25_kill_by_device() will happen. The corresponding
fail log is shown below:
===============================================================
BUG: KASAN: null-ptr-deref in ax25_device_event+0xfd/0x290
Call Trace:
...
ax25_device_event+0xfd/0x290
raw_notifier_call_chain+0x5e/0x70
dev_close_many+0x174/0x220
unregister_netdevice_many+0x1f7/0xa60
unregister_netdevice_queue+0x12f/0x170
unregister_netdev+0x13/0x20
mkiss_close+0xcd/0x140
tty_ldisc_release+0xc0/0x220
tty_release_struct+0x17/0xa0
tty_release+0x62d/0x670
...
This patch add condition check in ax25_kill_by_device(). If s->sk is
NULL, it will goto if branch to kill device.
Fixes: 4e0f718daf97 ("ax25: improve the incomplete fix to avoid UAF and NPD bugs")
Reported-by: Thomas Osterried <thomas@osterried.de>
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
The ax25_kill_by_device() will set s->ax25_dev = NULL and
call ax25_disconnect() to change states of ax25_cb and
sock, if we call ax25_bind() before ax25_kill_by_device().
However, if we call ax25_bind() again between the window of
ax25_kill_by_device() and ax25_dev_device_down(), the values
and states changed by ax25_kill_by_device() will be reassigned.
Finally, ax25_dev_device_down() will deallocate net_device.
If we dereference net_device in syscall functions such as
ax25_release(), ax25_sendmsg(), ax25_getsockopt(), ax25_getname()
and ax25_info_show(), a UAF bug will occur.
One of the possible race conditions is shown below:
(USE) | (FREE)
ax25_bind() |
| ax25_kill_by_device()
ax25_bind() |
ax25_connect() | ...
| ax25_dev_device_down()
| ...
| dev_put_track(dev, ...) //FREE
ax25_release() | ...
ax25_send_control() |
alloc_skb() //USE |
the corresponding fail log is shown below:
===============================================================
BUG: KASAN: use-after-free in ax25_send_control+0x43/0x210
...
Call Trace:
...
ax25_send_control+0x43/0x210
ax25_release+0x2db/0x3b0
__sock_release+0x6d/0x120
sock_close+0xf/0x20
__fput+0x11f/0x420
...
Allocated by task 1283:
...
__kasan_kmalloc+0x81/0xa0
alloc_netdev_mqs+0x5a/0x680
mkiss_open+0x6c/0x380
tty_ldisc_open+0x55/0x90
...
Freed by task 1969:
...
kfree+0xa3/0x2c0
device_release+0x54/0xe0
kobject_put+0xa5/0x120
tty_ldisc_kill+0x3e/0x80
...
In order to fix these UAF bugs caused by rebinding operation,
this patch adds dev_hold_track() into ax25_bind() and
corresponding dev_put_track() into ax25_kill_by_device().
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
The ax25_disconnect() in ax25_kill_by_device() is not
protected by any locks, thus there is a race condition
between ax25_disconnect() and ax25_destroy_socket().
when ax25->sk is assigned as NULL by ax25_destroy_socket(),
a NULL pointer dereference bug will occur if site (1) or (2)
dereferences ax25->sk.
ax25_kill_by_device() | ax25_release()
ax25_disconnect() | ax25_destroy_socket()
... |
if(ax25->sk != NULL) | ...
... | ax25->sk = NULL;
bh_lock_sock(ax25->sk); //(1) | ...
... |
bh_unlock_sock(ax25->sk); //(2)|
This patch moves ax25_disconnect() into lock_sock(), which can
synchronize with ax25_destroy_socket() in ax25_release().
Fail log:
===============================================================
BUG: kernel NULL pointer dereference, address: 0000000000000088
...
RIP: 0010:_raw_spin_lock+0x7e/0xd0
...
Call Trace:
ax25_disconnect+0xf6/0x220
ax25_device_event+0x187/0x250
raw_notifier_call_chain+0x5e/0x70
dev_close_many+0x17d/0x230
rollback_registered_many+0x1f1/0x950
unregister_netdevice_queue+0x133/0x200
unregister_netdev+0x13/0x20
...
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
The previous commit d01ffb9eee4a ("ax25: add refcount in ax25_dev
to avoid UAF bugs") introduces refcount into ax25_dev, but there
are reference leak paths in ax25_ctl_ioctl(), ax25_fwd_ioctl(),
ax25_rt_add(), ax25_rt_del() and ax25_rt_opt().
This patch uses ax25_dev_put() and adjusts the position of
ax25_addr_ax25dev() to fix reference cout leaks of ax25_dev.
Fixes: d01ffb9eee4a ("ax25: add refcount in ax25_dev to avoid UAF bugs")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20220203150811.42256-1-duoming@zju.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
If we dereference ax25_dev after we call kfree(ax25_dev) in
ax25_dev_device_down(), it will lead to concurrency UAF bugs.
There are eight syscall functions suffer from UAF bugs, include
ax25_bind(), ax25_release(), ax25_connect(), ax25_ioctl(),
ax25_getname(), ax25_sendmsg(), ax25_getsockopt() and
ax25_info_show().
One of the concurrency UAF can be shown as below:
(USE) | (FREE)
| ax25_device_event
| ax25_dev_device_down
ax25_bind | ...
... | kfree(ax25_dev)
ax25_fillin_cb() | ...
ax25_fillin_cb_from_dev() |
... |
The root cause of UAF bugs is that kfree(ax25_dev) in
ax25_dev_device_down() is not protected by any locks.
When ax25_dev, which there are still pointers point to,
is released, the concurrency UAF bug will happen.
This patch introduces refcount into ax25_dev in order to
guarantee that there are no pointers point to it when ax25_dev
is released.
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>