linux-kernel - Re: [PATCH] spi: spi-mem: check if data buffers are on stack

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Message-ID: <366bad2d-ebb3-a2a5-330d-ff9019d18733@microchip.com>
Date:   Tue, 1 Feb 2022 07:44:13 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <p.yadav@...com>, <broonie@...nel.org>
CC:     <michael@...le.cc>, <miquel.raynal@...tlin.com>,
        <tkuw584924@...il.com>, <linux-spi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] spi: spi-mem: check if data buffers are on stack

On 1/31/22 13:45, Pratyush Yadav wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> The buffers passed in the data phase must be DMA-able. Programmers often
> don't realise this requirement and pass in buffers that reside on the
> stack. This can be hard to spot when reviewing code. Reject ops if their
> data buffer is on the stack to avoid this.
> 
> Signed-off-by: Pratyush Yadav <p.yadav@...com>
> ---
>  drivers/spi/spi-mem.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index 37f4443ce9a0..b3793a2979ee 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -207,6 +207,15 @@ static int spi_mem_check_op(const struct spi_mem_op *op)
>             !spi_mem_buswidth_is_valid(op->data.buswidth))
>                 return -EINVAL;
> 
> +       /* Buffers must be DMA-able. */
> +       if (op->data.dir == SPI_MEM_DATA_IN &&
> +           object_is_on_stack(op->data.buf.in))

should we also check if the virt addr is valid?
if (object_is_on_stack(op->data.buf.in) || !virt_addr_valid(op->data.buf.in))