linux-kernel - [PATCH] iio: adc: at91-sama5d2_adc: Fix use-after-free in sama5d2

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Message-Id: <1c67249dbc78678c451a155c04ef908627da6d1a.1732776187.git.xiaopei01@kylinos.cn>
Date: Thu, 28 Nov 2024 14:45:50 +0800
From: Pei Xiao <xiaopei01@...inos.cn>
To: eugen.hristev@...aro.org,
	jic23@...nel.org,
	lars@...afoo.de,
	nicolas.ferre@...rochip.com,
	linux-iio@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	alexandre.belloni@...tlin.com
Cc: Pei Xiao <xiaopei01@...inos.cn>
Subject: [PATCH] iio: adc: at91-sama5d2_adc: Fix use-after-free in sama5d2_adc driver

at91_adc_interrupt can call at91_adc_touch_data_handler function
to start the work by schedule_work(&st->touch_st.workq).

If we remove the module which will call at91_adc_remove to
make cleanup, it will free indio_dev through iio_device_unregister
while the work mentioned above will be used. The sequence of operations
that may lead to a UAF bug is as follows:

CPU0                                      CPU1

                                     | at91_adc_workq_handler
at91_adc_remove                      |
iio_device_unregister(indio_dev)     |
device_release                       |
//free indio_dev                     |
                                     | iio_push_to_buffers(indio_dev)
                                     | //use indio_dev

Fix it by ensuring that the work is canceled before proceeding with
the cleanup in at91_adc_remove.

Fixes: 27e177190891 ("iio:adc:at91_adc8xx: introduce new atmel adc driver")
Signed-off-by: Pei Xiao <xiaopei01@...inos.cn>
---
 drivers/iio/adc/at91-sama5d2_adc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index 8e5aaf15a921..4ba52b500054 100644
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -2491,6 +2491,7 @@ static void at91_adc_remove(struct platform_device *pdev)
 	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
 	struct at91_adc_state *st = iio_priv(indio_dev);
 
+	cancel_work_sync(&st->touch_st.workq);
 	iio_device_unregister(indio_dev);
 
 	at91_adc_dma_disable(st);
-- 
2.34.1