[PATCH] spi: stm32: fix NULL check on pointer-to-pointer variable
Clement LE GOFFIC
clement.legoffic at foss.st.com
Mon Jun 30 00:34:13 PDT 2025
Hi Antonio,
On 6/28/25 02:02, Antonio Quartulli wrote:
> In stm32_spi_prepare_rx_dma_mdma_chaining() both rx_dma_desc
> and rx_mdma_desc are passed as pointer-to-pointer arguments.
>
> The goal is to pass back to the caller the value returned
> by dmaengine_prep_slave_sg(), when it is not NULL.
>
> However, the NULL check on the result is erroneously
> performed without dereferencing the pointer.
>
> Add the proper dereference operator to both checks.
>
> Fixes: d17dd2f1d8a1 ("spi: stm32: use STM32 DMA with STM32 MDMA to enhance DDR use")
> Addresses-Coverity-ID: 1644715 ("Null pointer dereferences (REVERSE_INULL)")
> Signed-off-by: Antonio Quartulli <antonio at mandelbit.com>
> ---
> drivers/spi/spi-stm32.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c
> index 3d20f09f1ae7..e9fa17e52fb0 100644
> --- a/drivers/spi/spi-stm32.c
> +++ b/drivers/spi/spi-stm32.c
> @@ -1529,7 +1529,7 @@ static int stm32_spi_prepare_rx_dma_mdma_chaining(struct stm32_spi *spi,
> DMA_PREP_INTERRUPT);
> sg_free_table(&dma_sgt);
>
> - if (!rx_dma_desc)
> + if (!*rx_dma_desc)
> return -EINVAL;
>
> /* Prepare MDMA slave_sg transfer MEM_TO_MEM (SRAM>DDR) */
> @@ -1563,8 +1563,8 @@ static int stm32_spi_prepare_rx_dma_mdma_chaining(struct stm32_spi *spi,
> DMA_PREP_INTERRUPT);
> sg_free_table(&mdma_sgt);
>
> - if (!rx_mdma_desc) {
> - rx_dma_desc = NULL;
> + if (!*rx_mdma_desc) {
> + *rx_dma_desc = NULL;
> return -EINVAL;
> }
>
Good catch for both pointers !
For readability, I would suggest to define two dma_async_tx_descriptor
ptr at the beginning of the function such as :
struct dma_async_tx_descriptor *_mdma_desc = *rx_mdma_desc;
struct dma_async_tx_descriptor *_dma_desc = *rx_dma_desc;
And then use them all along the function even in the assignation.
Best regards,
Clément
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