From 29b0589a865b6f66d141d79b2dd1373e4e50fe17 Mon Sep 17 00:00:00 2001

From: Duoming Zhou <duoming@zju.edu.cn>

Date: Tue, 24 Jan 2023 08:55:33 +0100

Subject: [PATCH] media: rc: Fix use-after-free bugs caused by ene_tx_irqsim()

Git-commit: 29b0589a865b6f66d141d79b2dd1373e4e50fe17

Patch-mainline: v6.3-rc1

References: CVE-2023-1118 bsc#1208837

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>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 drivers/media/rc/ene_ir.c | 3 ++-

 1 file changed, 2 insertions(+), 1 deletion(-)

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

@@ -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);

 }

-- 

2.35.3