[CVE-2023-4134] Input: cyttsp4_core - change del_timer_sync() to timer_shutdown_sync() - #808
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[ Upstream commit dbe8365 ] 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: 17fb156 ("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> Signed-off-by: Triet Hoang <triet.hoang@datalogic.com>
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[ Upstream commit dbe8365 ]
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: 17fb156 ("Input: cyttsp4 - add core driver for Cypress TMA4XX touchscreen devices")
Link: https://lore.kernel.org/r/20230421082919.8471-1-duoming@zju.edu.cn