FAILED: patch "[PATCH] iio: cros_ec: fix an use-after-free in" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 7771c8c80d62ad065637ef74ed2962983f6c5f6d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023101501-conclude-partner-77d5@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7771c8c80d62ad065637ef74ed2962983f6c5f6d Mon Sep 17 00:00:00 2001
From: Tzung-Bi Shih <[email protected]>
Date: Tue, 29 Aug 2023 11:06:22 +0800
Subject: [PATCH] iio: cros_ec: fix an use-after-free in
cros_ec_sensors_push_data()

cros_ec_sensors_push_data() reads indio_dev->active_scan_mask and calls iio_push_to_buffers_with_timestamp() without making sure the indio_dev stays in buffer mode. There is a race if indio_dev exits buffer mode right before cros_ec_sensors_push_data() accesses them.

An use-after-free on indio_dev->active_scan_mask was observed. The call trace:
[...]
_find_next_bit
cros_ec_sensors_push_data
cros_ec_sensorhub_event
blocking_notifier_call_chain
cros_ec_irq_thread

It was caused by a race condition: one thread just freed active_scan_mask at [1]; while another thread tried to access the memory at [2].

Fix it by calling iio_device_claim_buffer_mode() to ensure the indio_dev can't exit buffer mode during cros_ec_sensors_push_data().

[1]: https://elixir.bootlin.com/linux/v6.5/source/drivers/iio/industrialio-buffer.c#L1189
[2]: https://elixir.bootlin.com/linux/v6.5/source/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c#L198

index b72d39fc2434..6bfe5d6847e7 100644
@@ -190,8 +190,11 @@ int cros_ec_sensors_push_data(struct iio_dev *indio_dev,
 	/*
 	 * Ignore samples if the buffer is not set: it is needed if the ODR is
 	 * set but the buffer is not enabled yet.
+	 *
+	 * Note: iio_device_claim_buffer_mode() returns -EBUSY if the buffer
+	 * is not enabled.
 	 */
-	if (!iio_buffer_enabled(indio_dev))
+	if (iio_device_claim_buffer_mode(indio_dev) < 0)
 		return 0;
 
 	out = (s16 *)st->samples;

@@ -210,6 +213,7 @@ int cros_ec_sensors_push_data(struct iio_dev *indio_dev,
 	iio_push_to_buffers_with_timestamp(indio_dev, st->samples,
 					   timestamp + delta);
 
+	iio_device_release_buffer_mode(indio_dev);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(cros_ec_sensors_push_data);