Patch "media: rc: Fix use-after-free bugs caused by ene_tx_irqsim()" has been added to the 5.4-stable tree

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This is a note to let you know that I've just added the patch titled

    media: rc: Fix use-after-free bugs caused by ene_tx_irqsim()

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     media-rc-fix-use-after-free-bugs-caused-by-ene_tx_ir.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit cf44d2c21cc08920e1afef36e7777e0a57696d92
Author: Duoming Zhou <duoming@xxxxxxxxxx>
Date:   Tue Jan 24 08:55:33 2023 +0100

    media: rc: Fix use-after-free bugs caused by ene_tx_irqsim()
    
    [ Upstream commit 29b0589a865b6f66d141d79b2dd1373e4e50fe17 ]
    
    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)
                                   | 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@xxxxxxxx>
    
    Fixes: 9ea53b74df9c ("V4L/DVB: STAGING: remove lirc_ene0100 driver")
    Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
    Signed-off-by: Sean Young <sean@xxxxxxxx>
    Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/media/rc/ene_ir.c b/drivers/media/rc/ene_ir.c
index 82867a2a60b0e..20cadff242cf9 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);
 }
 



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