[PATCH v3] nvme: fix memory corruption for passthrough metadata

[Christoph Hellwig]

On Fri, Oct 13, 2023 at 07:49:19AM +0530, Kanchan Joshi wrote:
> > precedent to start doing it.
> In my mind, this was about dealing with the specific case when the
> kernel memory is being used for device DMA.
> We have just two cases: (i) separate meta buffer, and (ii) bounce
> buffer for data (+metadata).
> I had not planned sanity checks for user inputs for anything beyond that.
> As opposed to being preventive (in all cases), it was about failing
> only when we are certain that DMA will take place and it will corrupt
> kernel memory.
> 
> In the long-term, it may be possible for the path to do away with
> memory copies. The checks can disappear with that.

As soon as the user buffer is unaligned we need to bounce buffer,
including for the data buffer.