linux-stable/drivers/nfc/pn533
Lin Ma b8cedb7093 nfc: pn533: Fix buggy cleanup order
When removing the pn533 device (i2c or USB), there is a logic error. The
original code first cancels the worker (flush_delayed_work) and then
destroys the workqueue (destroy_workqueue), leaving the timer the last
one to be deleted (del_timer). This result in a possible race condition
in a multi-core preempt-able kernel. That is, if the cleanup
(pn53x_common_clean) is concurrently run with the timer handler
(pn533_listen_mode_timer), the timer can queue the poll_work to the
already destroyed workqueue, causing use-after-free.

This patch reorder the cleanup: it uses the del_timer_sync to make sure
the handler is finished before the routine will destroy the workqueue.
Note that the timer cannot be activated by the worker again.

static void pn533_wq_poll(struct work_struct *work)
...
 rc = pn533_send_poll_frame(dev);
 if (rc)
   return;

 if (cur_mod->len == 0 && dev->poll_mod_count > 1)
   mod_timer(&dev->listen_timer, ...);

That is, the mod_timer can be called only when pn533_send_poll_frame()
returns no error, which is impossible because the device is detaching
and the lower driver should return ENODEV code.

Signed-off-by: Lin Ma <linma@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
2022-05-18 13:58:13 +01:00
..
i2c.c nfc: pn533: Constify pn533_phy_ops 2021-10-07 13:35:10 +01:00
Kconfig treewide: replace '---help---' in Kconfig files with 'help' 2020-06-14 01:57:21 +09:00
Makefile nfc: pn533: add UART phy driver 2019-10-29 21:05:26 -07:00
pn533.c nfc: pn533: Fix buggy cleanup order 2022-05-18 13:58:13 +01:00
pn533.h nfc: pn533: Constify pn533_phy_ops 2021-10-07 13:35:10 +01:00
uart.c nfc: pn533: Constify pn533_phy_ops 2021-10-07 13:35:10 +01:00
usb.c nfc: pn533: Constify pn533_phy_ops 2021-10-07 13:35:10 +01:00