[PATCH v2] iio: accel: fxls8962af: Fix use after free in fxls8962af_fifo_flush

[Sean Nyekjaer]

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
synchronize_irq() to ensure that no interrupt is currently running when
disabling buffer mode.

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@xxxxxxxxxxxxxxx
Suggested-by: David Lechner <dlechner@xxxxxxxxxxxx>
Signed-off-by: Sean Nyekjaer <sean@xxxxxxxxxx>
---
Changes in v2:
- As per David's suggestion; switched to use synchronize_irq() instead.
- Link to v1: https://lore.kernel.org/r/20250524-fxlsrace-v1-1-dec506dc87ae@xxxxxxxxxx
---
 drivers/iio/accel/fxls8962af-core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iio/accel/fxls8962af-core.c b/drivers/iio/accel/fxls8962af-core.c
index 6d23da3e7aa22c61f2d9348bb91d70cc5719a732..f2558fba491dffa78b26d47d2cd9f1f4d9811f54 100644
--- a/drivers/iio/accel/fxls8962af-core.c
+++ b/drivers/iio/accel/fxls8962af-core.c
@@ -866,6 +866,8 @@ static int fxls8962af_buffer_predisable(struct iio_dev *indio_dev)
 	if (ret)
 		return ret;
 
+	synchronize_irq(data->irq);
+
 	ret = __fxls8962af_fifo_set_mode(data, false);
 
 	if (data->enable_event)

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

Best regards,
-- 
Sean Nyekjaer <sean@xxxxxxxxxx>