mirror of
https://github.com/hardkernel/linux.git
synced 2026-06-05 10:31:46 +09:00
1e7417c188
The timer dev->stat_monitor can schedule the delayed work dev->wq and
the delayed work dev->wq can also arm the dev->stat_monitor timer.
When the device is detaching, the net_device will be deallocated. but
the net_device private data could still be dereferenced in delayed work
or timer handler. As a result, the UAF bugs will happen.
One racy situation is shown below:
(Thread 1) | (Thread 2)
lan78xx_stat_monitor() |
... | lan78xx_disconnect()
lan78xx_defer_kevent() | ...
... | cancel_delayed_work_sync(&dev->wq);
schedule_delayed_work() | ...
(wait some time) | free_netdev(net); //free net_device
lan78xx_delayedwork() |
//use net_device private data |
dev-> //use |
Although we use cancel_delayed_work_sync() to cancel the delayed work
in lan78xx_disconnect(), it could still be scheduled in timer handler
lan78xx_stat_monitor().
Another racy situation is shown below:
(Thread 1) | (Thread 2)
lan78xx_delayedwork |
mod_timer() | lan78xx_disconnect()
| cancel_delayed_work_sync()
(wait some time) | if (timer_pending(&dev->stat_monitor))
| del_timer_sync(&dev->stat_monitor);
lan78xx_stat_monitor() | ...
lan78xx_defer_kevent() | free_netdev(net); //free
//use net_device private data|
dev-> //use |
Although we use del_timer_sync() to delete the timer, the function
timer_pending() returns 0 when the timer is activated. As a result,
the del_timer_sync() will not be executed and the timer could be
re-armed.
In order to mitigate this bug, We use timer_shutdown_sync() to shutdown
the timer and then use cancel_delayed_work_sync() to cancel the delayed
work. As a result, the net_device could be deallocated safely.
What's more, the dev->flags is set to EVENT_DEV_DISCONNECT in
lan78xx_disconnect(). But it could still be set to EVENT_STAT_UPDATE
in lan78xx_stat_monitor(). So this patch put the set_bit() behind
timer_shutdown_sync().
Fixes: 77dfff5bb7 ("lan78xx: Fix race condition in disconnect handling")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
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.