| Message ID | 20230124075533.30152-1-duoming@zju.edu.cn |
|---|---|
| State | Accepted |
| Commit | 29b0589a865b6f66d141d79b2dd1373e4e50fe17 |
| Headers | show |
| Series | [v3] media: rc: Fix use-after-free bugs caused by ene_tx_irqsim() | expand |
diff --git a/drivers/media/rc/ene_ir.c b/drivers/media/rc/ene_ir.c index e09270916fb..11ee21a7db8 100644 --- a/drivers/media/rc/ene_ir.c +++ b/drivers/media/rc/ene_ir.c @@ -1106,6 +1106,8 @@ static void ene_remove(struct pnp_dev *pnp_dev) struct ene_device *dev = pnp_get_drvdata(pnp_dev); unsigned long flags; + rc_unregister_device(dev->rdev); + del_timer_sync(&dev->tx_sim_timer); spin_lock_irqsave(&dev->hw_lock, flags); ene_rx_disable(dev); ene_rx_restore_hw_buffer(dev); @@ -1113,7 +1115,6 @@ static void ene_remove(struct pnp_dev *pnp_dev) free_irq(dev->irq, dev); release_region(dev->hw_io, ENE_IO_SIZE); - rc_unregister_device(dev->rdev); kfree(dev); }
When the ene device is detaching, function ene_remove() will be called. But there is no function to cancel tx_sim_timer in ene_remove(), the timer handler ene_tx_irqsim() could race with ene_remove(). As a result, the UAF bugs could happen, the process is shown below. (cleanup routine) | (timer routine) | mod_timer(&dev->tx_sim_timer, ..) ene_remove() | (wait a time) kfree(dev) //FREE | | ene_tx_irqsim() | dev->hw_lock //USE | ene_tx_sample(dev) //USE Fix by adding del_timer_sync(&dev->tx_sim_timer) in ene_remove(), The tx_sim_timer could stop before ene device is deallocated. What's more, The rc_unregister_device() and del_timer_sync() should be called first in ene_remove() and the deallocated functions such as free_irq(), release_region() and so on should be called behind them. Because the rc_unregister_device() is well synchronized. Otherwise, race conditions may happen. The situations that may lead to race conditions are shown below. Firstly, the rx receiver is disabled with ene_rx_disable() before rc_unregister_device() in ene_remove(), which means it can be enabled again if a process opens /dev/lirc0 between ene_rx_disable() and rc_unregister_device(). Secondly, the irqaction descriptor is freed by free_irq() before the rc device is unregistered, which means irqaction descriptor may be accessed again after it is deallocated. Thirdly, the timer can call ene_tx_sample() that can write to the io ports, which means the io ports could be accessed again after they are deallocated by release_region(). Therefore, the rc_unregister_device() and del_timer_sync() should be called first in ene_remove(). Suggested by: Sean Young <sean@mess.org> Fixes: 9ea53b74df9c ("V4L/DVB: STAGING: remove lirc_ene0100 driver") Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> --- Changes in v3: - Call rc_unregister_device() and del_timer_sync() first in ene_remove(). drivers/media/rc/ene_ir.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)