Re: [PATCH 3.2 108/221] spi: dw-mid: avoid potential NULL dereference

Luis Henriques
2015-05-06T10:25:10Z

On Tue, May 05, 2015 at 02:16:39AM +0100, Ben Hutchings wrote:
> 3.2.69-rc1 review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>
> commit c9dafb27c84412fe4b17c3b94cc4ffeef5df1833 upstream.
>
> When DMA descriptor allocation fails we should not try to assign any fields in
> the bad descriptor. The patch adds the necessary checks for that.
>
> Fixes: 7063c0d942a1 (spi/dw_spi: add DMA support)
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> [bwh: Backported to 3.2: adjust context]
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
> drivers/spi/spi-dw-mid.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> --- a/drivers/spi/spi-dw-mid.c
> +++ b/drivers/spi/spi-dw-mid.c
> @@ -155,6 +155,9 @@ static int mid_spi_dma_transfer(struct d
> 1,
> DMA_TO_DEVICE,
> DMA_PREP_INTERRUPT | DMA_COMPL_SKIP_DEST_UNMAP);
> + if (!txdesc)
> + return NULL;
> +

This backport doesn't look right to me as the function returns an int,
not a pointer. OTOH, it seems like this return value is not checked
anywhere, which is why I dropped this patch in the 3.16 kernel.

Cheers,
--
Luís

> txdesc->callback = dw_spi_dma_done;
> txdesc->callback_param = dws;
>
> @@ -177,6 +180,9 @@ static int mid_spi_dma_transfer(struct d
> 1,
> DMA_FROM_DEVICE,
> DMA_PREP_INTERRUPT | DMA_COMPL_SKIP_DEST_UNMAP);
> + if (!rxdesc)
> + return NULL;
> +
> rxdesc->callback = dw_spi_dma_done;
> rxdesc->callback_param = dws;
>
>
> --
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