CVE-2023-1118: Use After Free (CWE-416)
value: A flaw use after free in the Linux kernel integrated infrared receiver/transceiver driver was found in the way user detaching rc device. A local user could use this flaw to crash the system or potentially escalate their privileges on the system.
CWE description: The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
CVSS v3 base score: 7.8
Published: 2023-03-02T18:15Z
Repository: https://github.com/torvalds/linux
Language: C
Files changed: drivers/media/rc/ene_ir.c
Commit date: 2023-02-08 07:49:22 +0100
Commit message: media: rc: Fix use-after-free bugs caused by ene_tx_irqsim()

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@mess.org>

Fixes: 9ea53b74df9c ("V4L/DVB: STAGING: remove lirc_ene0100 driver")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Diff: diff --git a/drivers/media/rc/ene_ir.c b/drivers/media/rc/ene_ir.c
index e09270916fbc..11ee21a7db8f 100644
--- a/drivers/media/rc/ene_ir.c
+++ b/drivers/media/rc/ene_ir.c
@@ -1104,18 +1104,19 @@ static int ene_probe(struct pnp_dev *pnp_dev, const struct pnp_device_id *id)
 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);
 	spin_unlock_irqrestore(&dev->hw_lock, flags);
 
 	free_irq(dev->irq, dev);
 	release_region(dev->hw_io, ENE_IO_SIZE);
-	rc_unregister_device(dev->rdev);
 	kfree(dev);
 }
 
 /* enable wake on IR (wakes on specific button on original remote) */
 static void ene_enable_wake(struct ene_device *dev, bool enable)

Vulnerable code: 	rc_unregister_device(dev->rdev);
Fixed code: 	rc_unregister_device(dev->rdev);
	del_timer_sync(&dev->tx_sim_timer);