iio: adc: ad_sigma_delta: fix use-after-free on unbind

ad_sd_buffer_postenable() allocates sigma_delta->samples_buf with
devm_krealloc() at runtime, so its devres entry sits after all
probe-time entries of the driver. devm resources are released in
reverse allocation order, which means unbind frees samples_buf before
iio_device_unregister() disables the buffers and detaches the trigger
pollfunc. The data ready IRQ is still enabled at that point, so
ad_sd_trigger_handler() can still run and memcpy() incoming samples
into the freed samples_buf.

Fix this by preallocating the buffer in
devm_ad_sd_setup_buffer_and_trigger(), before the triggered buffer and
the IRQ are set up, so it is freed only after iio_device_unregister()
has drained the trigger handler via free_irq(). Size it for the worst
case of all sequencer slots being active; ad_sd_validate_scan_mask()
already caps the number of active channels at num_slots.

This issue was found by an in-house static analysis tool.

Fixes: 8bea9af887de ("iio: adc: ad_sigma_delta: Add sequencer support")
Cc: stable@vger.kernel.org
Co-developed-by: Song Li <songl@zju.edu.cn>
Signed-off-by: Song Li <songl@zju.edu.cn>
Signed-off-by: Fan Wu <fanwu01@zju.edu.cn>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>

0 files changed, 0 insertions, 0 deletions