[PATCH AUTOSEL 4.19 3/9] memstick: r592: Fix UAF bug in r592_remove due to race condition

[Sasha Levin]

From: Zheng Wang <zyytlz.wz@xxxxxxx>

[ Upstream commit 63264422785021704c39b38f65a78ab9e4a186d7 ]

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@xxxxxxx>
Link: https://lore.kernel.org/r/20230307164338.1246287-1-zyytlz.wz@xxxxxxx
Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/memstick/host/r592.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/memstick/host/r592.c b/drivers/memstick/host/r592.c
index 4728a42d54b88..edb1b5588b7a0 100644
--- a/drivers/memstick/host/r592.c
+++ b/drivers/memstick/host/r592.c
@@ -831,7 +831,7 @@ 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) {
-- 
2.39.2