linux-kernel - [PATCH] iio: accel: fxls8962af: Fix use after free in fxls8962af_fifo

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Message-Id: <20250524-fxlsrace-v1-1-dec506dc87ae@geanix.com>
Date: Sat, 24 May 2025 12:34:09 +0200
From: Sean Nyekjaer <sean@...nix.com>
To: Jonathan Cameron <jic23@...nel.org>, 
 David Lechner <dlechner@...libre.com>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 stable@...r.kernel.org, Sean Nyekjaer <sean@...nix.com>
Subject: [PATCH] iio: accel: fxls8962af: Fix use after free in
 fxls8962af_fifo_flush

fxls8962af_fifo_flush() uses indio_dev->active_scan_mask (with
iio_for_each_active_channel()) without making sure the indio_dev
stays in buffer mode.
There is a race if indio_dev exits buffer mode in the middle of the
interrupt that flushes the fifo. Fix this by calling
iio_device_claim_buffer_mode() to ensure indio_dev can't exit buffer
mode during the flush.

Unable to handle kernel NULL pointer dereference at virtual address 00000000 when read
[...]
_find_first_bit_le from fxls8962af_fifo_flush+0x17c/0x290
fxls8962af_fifo_flush from fxls8962af_interrupt+0x80/0x178
fxls8962af_interrupt from irq_thread_fn+0x1c/0x7c
irq_thread_fn from irq_thread+0x110/0x1f4
irq_thread from kthread+0xe0/0xfc
kthread from ret_from_fork+0x14/0x2c

Fixes: 79e3a5bdd9ef ("iio: accel: fxls8962af: add hw buffered sampling")
Cc: stable@...r.kernel.org
Signed-off-by: Sean Nyekjaer <sean@...nix.com>
---
 drivers/iio/accel/fxls8962af-core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/iio/accel/fxls8962af-core.c b/drivers/iio/accel/fxls8962af-core.c
index 6d23da3e7aa22c61f2d9348bb91d70cc5719a732..7db83ebeea823173d79bf8ff484add16f575edfc 100644
--- a/drivers/iio/accel/fxls8962af-core.c
+++ b/drivers/iio/accel/fxls8962af-core.c
@@ -973,6 +973,9 @@ static int fxls8962af_fifo_flush(struct iio_dev *indio_dev)
 	if (ret)
 		return ret;
 
+	if (iio_device_claim_buffer_mode(indio_dev) < 0)
+		return 0;
+
 	/* Demux hw FIFO into kfifo. */
 	for (i = 0; i < count; i++) {
 		int j, bit;
@@ -989,6 +992,8 @@ static int fxls8962af_fifo_flush(struct iio_dev *indio_dev)
 		tstamp += sample_period;
 	}
 
+	iio_device_release_buffer_mode(indio_dev);
+
 	return count;
 }
 

---
base-commit: 5c3fcb36c92443a9a037683626a2e43d8825f783
change-id: 20250524-fxlsrace-f4d20e29fb29

Best regards,
-- 
Sean Nyekjaer <sean@...nix.com>