Re: [PATCH v2] mmc: sdhci: Clear unused bounce buffer at DMA mmap error path

[Ulf Hansson]

On Fri, 11 Jun 2021 at 12:19, Takashi Iwai <tiwai@xxxxxxx> wrote:
>
> When DMA-mapping of the bounce buffer fails, the driver tries to fall
> back, but it leaves the allocated host->bounce_buffer although its
> size is zero.  Later on, the driver checks the use of bounce buffer
> with host->bounce_buffer pointer, and it tries to use the buffer
> incorrectly, resulting in Oops.
>
> This patch clears the release the unused buffer and clears the
> bounce_buffer pointer for addressing the problem.
>
> Acked-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>

Applied for fixes, thanks!

Kind regards
Uffe


> ---
> v1->v2: correct the device pointer to mmc_dev(mmc)
>
>  drivers/mmc/host/sdhci.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index bf238ade1602..c80bc6c4ebf3 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -4072,9 +4072,13 @@ static void sdhci_allocate_bounce_buffer(struct sdhci_host *host)
>                                            bounce_size,
>                                            DMA_BIDIRECTIONAL);
>         ret = dma_mapping_error(mmc_dev(mmc), host->bounce_addr);
> -       if (ret)
> +       if (ret) {
> +               devm_kfree(mmc_dev(mmc), host->bounce_buffer);
> +               host->bounce_buffer = NULL;
>                 /* Again fall back to max_segs == 1 */
>                 return;
> +       }
> +
>         host->bounce_buffer_size = bounce_size;
>
>         /* Lie about this since we're bouncing */
> --
> 2.26.2
>