linux-kernel - Re: [PATCH] mmc: warn for invalid SDIO data buffers【请注意，邮件由linux-mmc-owner@...r.kernel.org代发】

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Date:   Fri, 2 Jul 2021 16:15:41 +0800
From:   Shawn Lin <shawn.lin@...k-chips.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     shawn.lin@...k-chips.com,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH] mmc: warn for invalid SDIO data buffers【请注意，邮件由linux-mmc-owner@...r.kernel.org代发】

On 2021/7/2 15:03, Arnd Bergmann wrote:
> On Fri, Jul 2, 2021 at 3:02 AM Shawn Lin <shawn.lin@...k-chips.com> wrote:
>> On 2021/6/30 20:20, Arnd Bergmann wrote:
>>> From: Arnd Bergmann <arnd@...db.de>
>>>
>>> Jernej Skrabec reported a problem with the cw1200 driver failing on
>>> arm64 systems with CONFIG_VMAP_STACK=y.
>>>
>>> The driver in this case passes a pointer to a stack variable (in vmalloc
>>> space) into the sdio layer, which gets translated into an invalid DMA
>>> address.
>>>
>>> Even without CONFIG_VMAP_STACK, the driver is still unreliable, as
>>> cache invalidations on the DMA buffer may cause random data corruption
>>> in adjacent stack slots.
>>>
>>> This could be worked around in the SDIO core, but in the discussion we
>>> decided that passing a stack variable into SDIO should always be considered
>>> a bug, as it is for USB drivers.
>>>
>>> Change the sdio core to produce a one-time warning for any on-stack
>>> (both with and without CONFIG_VMAP_STACK) as well as any vmalloc
>>> or module-local address that would have the same translation problem.
>>
>> This was the previous comment about the same topic.
>> Should we check for mmc_io_rw_direct?
>>
>> https://www.spinics.net/lists/linux-mmc/msg41794.html
> 
> Hi Shawn,
> 
> thank you for remembering that previous discussion, that is a
> good question. Looking at the code though, I don't actually
> see any part of mmc_io_rw_direct() doing DMA on a caller-provided
> buffer. The only thing I see in the code is a 'u8 *out' argument, but
> that is just a pointer to a single byte that is set by this function.
> 

I didn't quite get the point we need check out for
mmc_io_rw_direct() either. As I thought what Ulf was suggesting was some
controllers might use data fifo to get cmd response and get DMA
involved? But I don't see a explicit one.

> Do you see any other issue with that function, or does that mean
> we don't have to change it?
> 
>         Arnd
> 
> 
>