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5352a76130
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: 9fd75b66b8 ("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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.