linux-kernel - Re: [PATCH] spi/xilinx: Fix access invalid memory on xilinx_spi

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Date:	Fri, 30 Jan 2015 11:06:32 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:	Mark Brown <broonie@...nel.org>,
	Michal Simek <michal.simek@...inx.com>,
	Sören Brinkmann <soren.brinkmann@...inx.com>,
	linux-spi <linux-spi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] spi/xilinx: Fix access invalid memory on xilinx_spi_tx

Hi Ricardo,

On Fri, Jan 30, 2015 at 7:10 AM, Ricardo Ribalda Delgado
<ricardo.ribalda@...il.com> wrote:
> On 1 and 2 bytes per word, the transfer of the 3 last bytes will access
> memory outside rx_ptr.
>
> Although this has not trigger any error on real hardware, we should
> better fix this.
>
> Fixes: 24ba5e593f391507 Remove rx_fn and tx_fn pointer
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
> ---
>  drivers/spi/spi-xilinx.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi-xilinx.c b/drivers/spi/spi-xilinx.c
> index 2ca55f6..a1b664d 100644
> --- a/drivers/spi/spi-xilinx.c
> +++ b/drivers/spi/spi-xilinx.c
> @@ -97,11 +97,26 @@ struct xilinx_spi {
>
>  static void xilinx_spi_tx(struct xilinx_spi *xspi)
>  {
> +       u32 data = 0;
> +
>         if (!xspi->tx_ptr) {
>                 xspi->write_fn(0, xspi->regs + XSPI_TXD_OFFSET);
>                 return;
>         }
> -       xspi->write_fn(*(u32 *)(xspi->tx_ptr), xspi->regs + XSPI_TXD_OFFSET);
> +
> +       switch (xspi->bytes_per_word) {
> +       case 1:
> +               data = *(u8 *)(xspi->rx_ptr);
> +               break;
> +       case 2:
> +               data = *(u16 *)(xspi->rx_ptr);
> +               break;
> +       case 4:
> +               data = *(u32 *)(xspi->rx_ptr);
> +               break;
> +       }
> +
> +       xspi->write_fn(data, xspi->regs + XSPI_TXD_OFFSET);

Is this endian-safe?

>         xspi->tx_ptr += xspi->bytes_per_word;
>  }

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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