memstick: r592: Fix UAF bug in r592_remove due to race condition

In r592_probe, dev->detect_timer was bound with r592_detect_timer.
In r592_irq function, the timer function will be invoked by mod_timer.

If we remove the module which will call hantro_release to make cleanup,
there may be a unfinished work. The possible sequence is as follows,
which will cause a typical UAF bug.

Fix it by canceling the work before cleanup in r592_remove.

CPU0                  CPU1

                    |r592_detect_timer
r592_remove         |
  memstick_free_host|
  put_device;       |
  kfree(host);      |
                    |
                    | queue_work
                    |   &host->media_checker //use

Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Link: https://lore.kernel.org/r/20230307164338.1246287-1-zyytlz.wz@163.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/memstick/host/r592.c b/drivers/memstick/host/r592.c
index 1d35d14..42bfc46 100644 (file)
--- a/drivers/memstick/host/r592.c
+++ b/drivers/memstick/host/r592.c
@@ -829,7 +829,7 @@ static void r592_remove(struct pci_dev *pdev)
        /* Stop the processing thread.
        That ensures that we won't take any more requests */
        kthread_stop(dev->io_thread);
-
+       del_timer_sync(&dev->detect_timer);
        r592_enable_device(dev, false);
 
        while (!error && dev->req) {