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Message-ID: <69f14b04-2ffe-95e3-c6a2-ee6f2628144a@rock-chips.com>
Date:   Fri, 2 Jul 2021 16:15:41 +0800
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Cc:     shawn.lin@rock-chips.com,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        linux-mmc <linux-mmc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>
Subject: =?UTF-8?Q?Re=3a_=5bPATCH=5d_mmc=3a_warn_for_invalid_SDIO_data_buffe?=
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To:     Arnd Bergmann <arnd@kernel.org>
References: <20210630122057.2795882-1-arnd@kernel.org>
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 <CAK8P3a3UjLfKpsg2M-RP3AO3CVCnZrbD71uaLf0+iiJ9RJsHCQ@mail.gmail.com>
From:   Shawn Lin <shawn.lin@rock-chips.com>
In-Reply-To: <CAK8P3a3UjLfKpsg2M-RP3AO3CVCnZrbD71uaLf0+iiJ9RJsHCQ@mail.gmail.com>
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On 2021/7/2 15:03, Arnd Bergmann wrote:
> On Fri, Jul 2, 2021 at 3:02 AM Shawn Lin <shawn.lin@rock-chips.com> wrote:
>> On 2021/6/30 20:20, Arnd Bergmann wrote:
>>> From: Arnd Bergmann <arnd@arndb.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
> 
> 
>