linux-kernel - Re: [PATCH v2] iio: accel: fxls8962af: Fix use after free in fxls8962af_fifo

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Message-ID: <b1f0dbee-13bd-4e5c-90b9-c6d88cb15971@baylibre.com>
Date: Tue, 3 Jun 2025 08:29:51 -0500
From: David Lechner <dlechner@...libre.com>
To: Sean Nyekjaer <sean@...nix.com>, Jonathan Cameron <jic23@...nel.org>,
 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
Subject: Re: [PATCH v2] iio: accel: fxls8962af: Fix use after free in
 fxls8962af_fifo_flush

On 6/3/25 7:25 AM, Sean Nyekjaer wrote:
> 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@...r.kernel.org
> Suggested-by: David Lechner <dlechner@...libre.com>
> Signed-off-by: Sean Nyekjaer <sean@...nix.com>
> ---
> 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@geanix.com
Were you able to find a way to reproduce the bug well enough to
test this?