Re: [PATCH] spi: stm32: drop devres version of spi_register_master

Hi Lukas,

On Tue, Mar 16, 2021 at 10:17:44PM +0100, Lukas Wunner wrote:

On Fri, Mar 12, 2021 at 11:34:46AM +0100, Alain Volmat wrote:

quoted

--- a/drivers/spi/spi-stm32.c
+++ b/drivers/spi/spi-stm32.c

@@ -1960,6 +1960,7 @@ static int stm32_spi_remove(struct platform_device *pdev)
 	struct spi_master *master = platform_get_drvdata(pdev);
 	struct stm32_spi *spi = spi_master_get_devdata(master);
 
+	spi_unregister_master(master);
 	spi->cfg->disable(spi);
 
 	if (master->dma_tx)

This introduces a use-after-free because spi_unregister_master()
drops the last reference on the spi_master allocation (which includes
the struct stm32_spi), causing it to be freed, yet the stm32_spi
struct is accessed afterwards.

Indeed. Thanks. I've fixed that and will post it.

You need to convert the driver to devm_spi_alloc_master() to
fix the use-after-free.  See commit 6cfd39e212de for an example.

Thanks,

Lukas

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