| Message ID | 20230421082919.8471-1-duoming@zju.edu.cn |
|---|---|
| State | Accepted |
| Commit | dbe836576f12743a7d2d170ad4ad4fd324c4d47a |
| Headers | show |
| Series | Input: cyttsp4_core - change del_timer_sync() to timer_shutdown_sync() | expand |
On Fri, Apr 21, 2023 at 04:29:19PM +0800, Duoming Zhou wrote: > 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: 17fb1563d69b ("Input: cyttsp4 - add core driver for Cypress TMA4XX touchscreen devices") > Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> Applied, thank you.
diff --git a/drivers/input/touchscreen/cyttsp4_core.c b/drivers/input/touchscreen/cyttsp4_core.c index 0cd6f626ade..7cb26929dc7 100644 --- a/drivers/input/touchscreen/cyttsp4_core.c +++ b/drivers/input/touchscreen/cyttsp4_core.c @@ -1263,9 +1263,8 @@ static void cyttsp4_stop_wd_timer(struct cyttsp4 *cd) * Ensure we wait until the watchdog timer * running on a different CPU finishes */ - del_timer_sync(&cd->watchdog_timer); + timer_shutdown_sync(&cd->watchdog_timer); cancel_work_sync(&cd->watchdog_work); - del_timer_sync(&cd->watchdog_timer); } static void cyttsp4_watchdog_timer(struct timer_list *t)
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: 17fb1563d69b ("Input: cyttsp4 - add core driver for Cypress TMA4XX touchscreen devices") Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> --- drivers/input/touchscreen/cyttsp4_core.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)