linux-kernel - Re: spi: stm32-qspi: Update spi registering

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Date:   Sat, 8 Jan 2022 20:48:19 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     patrice.chotard@...s.st.com
Cc:     Mark Brown <broonie@...nel.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        linux-spi@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        christophe.kerello@...s.st.com
Subject: Re: spi: stm32-qspi: Update spi registering

On Thu, Jan 06, 2022 at 02:20:52PM +0100, patrice.chotard@...s.st.com wrote:
> --- a/drivers/spi/spi-stm32-qspi.c
> +++ b/drivers/spi/spi-stm32-qspi.c
> @@ -784,7 +784,7 @@ static int stm32_qspi_probe(struct platform_device *pdev)
>  	pm_runtime_enable(dev);
>  	pm_runtime_get_noresume(dev);
>  
> -	ret = devm_spi_register_master(dev, ctrl);
> +	ret = spi_register_master(ctrl);
>  	if (ret)
>  		goto err_pm_runtime_free;
>  
> @@ -817,6 +817,7 @@ static int stm32_qspi_remove(struct platform_device *pdev)
>  	struct stm32_qspi *qspi = platform_get_drvdata(pdev);
>  
>  	pm_runtime_get_sync(qspi->dev);
> +	spi_unregister_master(qspi->ctrl);
>  	/* disable qspi */
>  	writel_relaxed(0, qspi->io_base + QSPI_CR);
>  	stm32_qspi_dma_free(qspi);

NAK, this introduces a use-after-free because the "qspi" allocation
is freed by spi_unregister_master(), yet is subsequently accessed.

You need to convert the driver to devm_spi_alloc_master() to avoid that.
Do it in the same patch to ease backporting.

Please add a stable designation and a Fixes: tag.  Chances are the patch
needs to be backported all the way back to the release when the driver
was first introduced.

Thanks,

Lukas