Re: [PATCH spi] spi: spi-fsl-lpspi: fix teardown order issue (UAF)

[Frank Li]

On Thu, Mar 19, 2026 at 07:38:12PM +0100, Marc Kleine-Budde wrote:
> There is a teardown order issue in the driver. The SPI controller is
> registered using devm_spi_register_controller(), which delays
> unregistration of the SPI controller until after the fsl_lpspi_remove()
> function returns.
>
> As the fsl_lpspi_remove() function synchronously tears down the DMA
> channels, a running SPI transfer triggers the following NULL pointer
> dereference due to use after free:
>
> | fsl_lpspi 42550000.spi: I/O Error in DMA RX
> | Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> [...]
> | Call trace:
> |  fsl_lpspi_dma_transfer+0x260/0x340 [spi_fsl_lpspi]
> |  fsl_lpspi_transfer_one+0x198/0x448 [spi_fsl_lpspi]
> |  spi_transfer_one_message+0x49c/0x7c8
> |  __spi_pump_transfer_message+0x120/0x420
> |  __spi_sync+0x2c4/0x520
> |  spi_sync+0x34/0x60
> |  spidev_message+0x20c/0x378 [spidev]
> |  spidev_ioctl+0x398/0x750 [spidev]
> [...]
>
> Switch from devm_spi_register_controller() to spi_register_controller() in
> fsl_lpspi_probe() and add the corresponding spi_unregister_controller() in
> fsl_lpspi_remove().

Feel like it is not correct's fix. devm_spi_register_controller() is quite
common, other SPI controller should have similar problem.

Frank
>
> Fixes: 5314987de5e5 ("spi: imx: add lpspi bus driver")
> Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
> ---
>  drivers/spi/spi-fsl-lpspi.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
> index b361c1bb3e43..45390e9b8cae 100644
> --- a/drivers/spi/spi-fsl-lpspi.c
> +++ b/drivers/spi/spi-fsl-lpspi.c
> @@ -1009,7 +1009,7 @@ static int fsl_lpspi_probe(struct platform_device *pdev)
>  		enable_irq(irq);
>  	}
>
> -	ret = devm_spi_register_controller(&pdev->dev, controller);
> +	ret = spi_register_controller(controller);
>  	if (ret < 0) {
>  		dev_err_probe(&pdev->dev, ret, "spi_register_controller error\n");
>  		goto free_dma;
> @@ -1035,6 +1035,7 @@ static void fsl_lpspi_remove(struct platform_device *pdev)
>  	struct fsl_lpspi_data *fsl_lpspi =
>  				spi_controller_get_devdata(controller);
>
> +	spi_unregister_controller(controller);
>  	fsl_lpspi_dma_exit(controller);
>
>  	pm_runtime_dont_use_autosuspend(fsl_lpspi->dev);
>
> ---
> base-commit: 8c89a077ca796a2fe248c584e9d7e66cff0388c8
> change-id: 20260319-spi-fsl-lpspi-fixes-725c6653c745
>
> Best regards,
> --
> Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
>