<feed xmlns='http://www.w3.org/2005/Atom'>
<title>user/sven/linux.git, branch v4.19.240</title>
<subtitle>Linux Kernel
</subtitle>
<id>https://git.stealer.net/cgit.cgi/user/sven/linux.git/atom?h=v4.19.240</id>
<link rel='self' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/atom?h=v4.19.240'/>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/'/>
<updated>2022-04-27T11:39:46Z</updated>
<entry>
<title>Linux 4.19.240</title>
<updated>2022-04-27T11:39:46Z</updated>
<author>
<name>Greg Kroah-Hartman</name>
<email>gregkh@linuxfoundation.org</email>
</author>
<published>2022-04-27T11:39:46Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=d54b97b3395ed8eb2c75acaecd4c62d66f9f126d'/>
<id>urn:sha1:d54b97b3395ed8eb2c75acaecd4c62d66f9f126d</id>
<content type='text'>
Link: https://lore.kernel.org/r/20220426081735.651926456@linuxfoundation.org
Tested-by: Jon Hunter &lt;jonathanh@nvidia.com&gt;
Tested-by: Guenter Roeck &lt;linux@roeck-us.net&gt;
Tested-by: Shuah Khan &lt;skhan@linuxfoundation.org&gt;
Tested-by: Hulk Robot &lt;hulkrobot@huawei.com&gt;
Tested-by: Linux Kernel Functional Testing &lt;lkft@linaro.org&gt;
Tested-by: Sudip Mukherjee &lt;sudip.mukherjee@codethink.co.uk&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>Revert "net: micrel: fix KS8851_MLL Kconfig"</title>
<updated>2022-04-27T11:39:46Z</updated>
<author>
<name>Marek Vasut</name>
<email>marex@denx.de</email>
</author>
<published>2022-04-25T21:48:59Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=92c7cca039098ade981858011f0e710e87dfbb31'/>
<id>urn:sha1:92c7cca039098ade981858011f0e710e87dfbb31</id>
<content type='text'>
This reverts commit 05b4c37fca84976ab9e3873d36fe53cd88d45408 which is
commit c3efcedd272aa6dd5929e20cf902a52ddaa1197a upstream.

The upstream commit c3efcedd272a ("net: micrel: fix KS8851_MLL Kconfig")
depends on e5f31552674e ("ethernet: fix PTP_1588_CLOCK dependencies")
which is not part of Linux 4.19.y . Revert the aforementioned commit to
prevent breakage in 4.19.y .

Signed-off-by: Marek Vasut &lt;marex@denx.de&gt;
Cc: David S. Miller &lt;davem@davemloft.net&gt;
Cc: Jakub Kicinski &lt;kuba@kernel.org&gt;
Cc: Paolo Abeni &lt;pabeni@redhat.com&gt;
Cc: Randy Dunlap &lt;rdunlap@infradead.org&gt;
Cc: Sasha Levin &lt;sashal@kernel.org&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>ax25: Fix UAF bugs in ax25 timers</title>
<updated>2022-04-27T11:39:46Z</updated>
<author>
<name>Duoming Zhou</name>
<email>duoming@zju.edu.cn</email>
</author>
<published>2022-04-21T10:24:22Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=3082f32c45465b692c314131c2a3657e0c23e09d'/>
<id>urn:sha1:3082f32c45465b692c314131c2a3657e0c23e09d</id>
<content type='text'>
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(&amp;ax25-&gt;t1timer,..)     |
                                    | ax25_release()
   (wait a time)                    |  ...
                                    |  ax25_dev_put(ax25_dev) //(4)FREE
   ax25_t1timer_expiry()            |
    ax25-&gt;ax25_dev-&gt;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 &lt;duoming@zju.edu.cn&gt;
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
[OP: backport to 4.19: adjust context]
Signed-off-by: Ovidiu Panait &lt;ovidiu.panait@windriver.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>ax25: Fix NULL pointer dereferences in ax25 timers</title>
<updated>2022-04-27T11:39:46Z</updated>
<author>
<name>Duoming Zhou</name>
<email>duoming@zju.edu.cn</email>
</author>
<published>2022-04-21T10:24:21Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=512f09df261b51b088f17d86dbdf300a3492523d'/>
<id>urn:sha1:512f09df261b51b088f17d86dbdf300a3492523d</id>
<content type='text'>
commit fc6d01ff9ef03b66d4a3a23b46fc3c3d8cf92009 upstream.

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(&amp;ax25-&gt;t1timer,..)     |
                                    | ax25_kill_by_device()
   (wait a time)                    |  ...
                                    |  s-&gt;ax25_dev = NULL; //(1)
   ax25_t1timer_expiry()            |
    ax25-&gt;ax25_dev-&gt;values[..] //(2)|  ...
     ...                            |

We set null to ax25_cb-&gt;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-&gt;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-&gt;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-&gt;ax25_dev in ax25_kill_by_device().

Fixes: 7ec02f5ac8a5 ("ax25: fix NPD bug in ax25_disconnect")
Signed-off-by: Duoming Zhou &lt;duoming@zju.edu.cn&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
[OP: backport to 4.19: adjust context]
Signed-off-by: Ovidiu Panait &lt;ovidiu.panait@windriver.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>ax25: fix NPD bug in ax25_disconnect</title>
<updated>2022-04-27T11:39:46Z</updated>
<author>
<name>Duoming Zhou</name>
<email>duoming@zju.edu.cn</email>
</author>
<published>2022-04-21T10:24:20Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=cb18d72179bf42a6ccd2b311739017b0ba9bc26e'/>
<id>urn:sha1:cb18d72179bf42a6ccd2b311739017b0ba9bc26e</id>
<content type='text'>
commit 7ec02f5ac8a5be5a3f20611731243dc5e1d9ba10 upstream.

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-&gt;sk is assigned as NULL by ax25_destroy_socket(),
a NULL pointer dereference bug will occur if site (1) or (2)
dereferences ax25-&gt;sk.

ax25_kill_by_device()                | ax25_release()
  ax25_disconnect()                  |   ax25_destroy_socket()
    ...                              |
    if(ax25-&gt;sk != NULL)             |     ...
      ...                            |     ax25-&gt;sk = NULL;
      bh_lock_sock(ax25-&gt;sk); //(1)  |     ...
      ...                            |
      bh_unlock_sock(ax25-&gt;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 &lt;duoming@zju.edu.cn&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
[OP: backport to 4.19: adjust context]
Signed-off-by: Ovidiu Panait &lt;ovidiu.panait@windriver.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>ax25: fix UAF bug in ax25_send_control()</title>
<updated>2022-04-27T11:39:46Z</updated>
<author>
<name>Duoming Zhou</name>
<email>duoming@zju.edu.cn</email>
</author>
<published>2022-04-21T10:24:19Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=1bf1b2a8a2caf9bc0d3cf1aa903a8dcaaa4371d0'/>
<id>urn:sha1:1bf1b2a8a2caf9bc0d3cf1aa903a8dcaaa4371d0</id>
<content type='text'>
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-&gt;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 &lt;duoming@zju.edu.cn&gt;
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
[OP: backport to 4.19: adjust dev_put_track()-&gt;dev_put()]
Signed-off-by: Ovidiu Panait &lt;ovidiu.panait@windriver.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>ax25: Fix refcount leaks caused by ax25_cb_del()</title>
<updated>2022-04-27T11:39:45Z</updated>
<author>
<name>Duoming Zhou</name>
<email>duoming@zju.edu.cn</email>
</author>
<published>2022-04-21T10:24:18Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=de55a1338e6a48ff1e41ea8db1432496fbe2a62b'/>
<id>urn:sha1:de55a1338e6a48ff1e41ea8db1432496fbe2a62b</id>
<content type='text'>
commit 9fd75b66b8f68498454d685dc4ba13192ae069b0 upstream.

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, &amp;ax25_list) {      |
  if (s-&gt;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-&gt;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 &lt;thomas@osterried.de&gt;
Signed-off-by: Duoming Zhou &lt;duoming@zju.edu.cn&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
[OP: backport to 4.19: adjust dev_put_track()-&gt;dev_put()]
Signed-off-by: Ovidiu Panait &lt;ovidiu.panait@windriver.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>ax25: fix UAF bugs of net_device caused by rebinding operation</title>
<updated>2022-04-27T11:39:45Z</updated>
<author>
<name>Duoming Zhou</name>
<email>duoming@zju.edu.cn</email>
</author>
<published>2022-04-21T10:24:17Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=b1e0a6fc7f17500484c402ad1cd018c24dfc14b3'/>
<id>urn:sha1:b1e0a6fc7f17500484c402ad1cd018c24dfc14b3</id>
<content type='text'>
commit feef318c855a361a1eccd880f33e88c460eb63b4 upstream.

The ax25_kill_by_device() will set s-&gt;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 &lt;duoming@zju.edu.cn&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
[OP: backport to 4.19: adjust dev_put_track()-&gt;dev_put() and
dev_hold_track()-&gt;dev_hold()]
Signed-off-by: Ovidiu Panait &lt;ovidiu.panait@windriver.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>ax25: fix reference count leaks of ax25_dev</title>
<updated>2022-04-27T11:39:45Z</updated>
<author>
<name>Duoming Zhou</name>
<email>duoming@zju.edu.cn</email>
</author>
<published>2022-04-21T10:24:16Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=a518be5772d36fcd0e4815d156e06feb137aad82'/>
<id>urn:sha1:a518be5772d36fcd0e4815d156e06feb137aad82</id>
<content type='text'>
commit 87563a043cef044fed5db7967a75741cc16ad2b1 upstream.

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 &lt;duoming@zju.edu.cn&gt;
Reviewed-by: Dan Carpenter &lt;dan.carpenter@oracle.com&gt;
Link: https://lore.kernel.org/r/20220203150811.42256-1-duoming@zju.edu.cn
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
[OP: backport to 4.19: adjust context]
Signed-off-by: Ovidiu Panait &lt;ovidiu.panait@windriver.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>ax25: add refcount in ax25_dev to avoid UAF bugs</title>
<updated>2022-04-27T11:39:45Z</updated>
<author>
<name>Duoming Zhou</name>
<email>duoming@zju.edu.cn</email>
</author>
<published>2022-04-21T10:24:15Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=e2b558fe507a1ed4c43db2b0057fc6e41f20a14c'/>
<id>urn:sha1:e2b558fe507a1ed4c43db2b0057fc6e41f20a14c</id>
<content type='text'>
commit d01ffb9eee4af165d83b08dd73ebdf9fe94a519b upstream.

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 &lt;duoming@zju.edu.cn&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
[OP: backport to 4.19: adjusted context]
Signed-off-by: Ovidiu Panait &lt;ovidiu.panait@windriver.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
</feed>
