Re: [PATCH AUTOSEL 5.8 28/29] spi: fsl-dspi: fix use-after-free in remove path

Sascha Hauer
2020-09-29T06:22:26Z

Hi Sasha,

On Mon, Sep 28, 2020 at 09:30:25PM -0400, Sasha Levin wrote:
> From: Sascha Hauer <s.hauer@pengutronix.de>
>
> [ Upstream commit 530b5affc675ade5db4a03f04ed7cd66806c8a1a ]
>
> spi_unregister_controller() not only unregisters the controller, but
> also frees the controller. This will free the driver data with it, so
> we must not access it later dspi_remove().
>
> Solve this by allocating the driver data separately from the SPI
> controller.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> Link: https://lore.kernel.org/r/20200923131026.20707-1-s.hauer@pengutronix.de
> Signed-off-by: Mark Brown <broonie@kernel.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> drivers/spi/spi-fsl-dspi.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)

This patch causes a regression and shouldn't be applied without the fix
in https://lkml.org/lkml/2020/9/28/300.

Sascha

> index 91c6affe139c9..aae9f9a7aea6c 100644
> --- a/drivers/spi/spi-fsl-dspi.c
> +++ b/drivers/spi/spi-fsl-dspi.c
> @@ -1273,11 +1273,14 @@ static int dspi_probe(struct platform_device *pdev)
> void __iomem *base;
> bool big_endian;
>
> - ctlr = spi_alloc_master(&pdev->dev, sizeof(struct fsl_dspi));
> + dspi = devm_kzalloc(&pdev->dev, sizeof(*dspi), GFP_KERNEL);
> + if (!dspi)
> + return -ENOMEM;
> +
> + ctlr = spi_alloc_master(&pdev->dev, 0);
> if (!ctlr)
> return -ENOMEM;
>
> - dspi = spi_controller_get_devdata(ctlr);
> dspi->pdev = pdev;
> dspi->ctlr = ctlr;
>
> @@ -1414,7 +1417,7 @@ static int dspi_probe(struct platform_device *pdev)
> if (dspi->devtype_data->trans_mode != DSPI_DMA_MODE)
> ctlr->ptp_sts_supported = true;
>
> - platform_set_drvdata(pdev, ctlr);
> + platform_set_drvdata(pdev, dspi);
>
> ret = spi_register_controller(ctlr);
> if (ret != 0) {
> @@ -1437,8 +1440,7 @@ static int dspi_probe(struct platform_device *pdev)
>
> static int dspi_remove(struct platform_device *pdev)
> {
> - struct spi_controller *ctlr = platform_get_drvdata(pdev);
> - struct fsl_dspi *dspi = spi_controller_get_devdata(ctlr);
> + struct fsl_dspi *dspi = platform_get_drvdata(pdev);
>
> /* Disconnect from the SPI framework */
> spi_unregister_controller(dspi->ctlr);
> --
> 2.25.1
>
>

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