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dbe836576f
The watchdog_timer can schedule tx_timeout_task and watchdog_work
can also arm watchdog_timer. The process is shown below:
----------- timer schedules work ------------
cyttsp4_watchdog_timer() //timer handler
schedule_work(&cd->watchdog_work)
----------- work arms timer ------------
cyttsp4_watchdog_work() //workqueue callback function
cyttsp4_start_wd_timer()
mod_timer(&cd->watchdog_timer, ...)
Although del_timer_sync() and cancel_work_sync() are called in
cyttsp4_remove(), the timer and workqueue could still be rearmed.
As a result, the possible use after free bugs could happen. The
process is shown below:
(cleanup routine) | (timer and workqueue routine)
cyttsp4_remove() | cyttsp4_watchdog_timer() //timer
cyttsp4_stop_wd_timer() | schedule_work()
del_timer_sync() |
| cyttsp4_watchdog_work() //worker
| cyttsp4_start_wd_timer()
| mod_timer()
cancel_work_sync() |
| cyttsp4_watchdog_timer() //timer
| schedule_work()
del_timer_sync() |
kfree(cd) //FREE |
| cyttsp4_watchdog_work() // reschedule!
| cd-> //USE
This patch changes del_timer_sync() to timer_shutdown_sync(),
which could prevent rearming of the timer from the workqueue.
Fixes: 17fb1563d6 ("Input: cyttsp4 - add core driver for Cypress TMA4XX touchscreen devices")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://lore.kernel.org/r/20230421082919.8471-1-duoming@zju.edu.cn
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.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.