Re: [PATCH v4] mmc: sdio: check the buffer address for sdio API

[Christoph Hellwig <hch@infradead.org>]

On Tue, Feb 07, 2017 at 08:54:50AM +0800, Shawn Lin wrote:
> It's fine if the host driver use PIO mode to transfer the
> vmalloc area buffer but not for DMA mode. The sdio APIs haven't
> provide the capability to tell the caller whether it will use DMA
> to finish the IO transfer or not,

Wether you dma or pio does not matter.  Addressability requirements
are slightly different, but it's nothing your patch is going to help
with.

> so don't give the randomly
> insmoded sdio function driver the possibility to break the kernel.
> Also the APIs shouldn't take the liberty to do a copy for these
> cases and just kick out these requests should be enough.
> 
> This issue is observed by doing insmod a downloaded wifi module
> driver and the kernel panic right away. Unfortunately we don't have
> the source code but adding this patch that it proves that the module
> driver was passing on a vmalloc area buffer for sdio APIs.

So don't use that illegally redistributed driver.  Working around it
is certainly nothing the upstream kernel cares about at all.