[PATCH v4] nvme: fix corruption for passthrough meta/data

[Keith Busch]

On Thu, Oct 26, 2023 at 08:03:30PM +0530, Kanchan Joshi wrote:
> On Mon, Oct 16, 2023 at 11:16 AM Christoph Hellwig <hch at lst.de> wrote:
> >
> > On Mon, Oct 16, 2023 at 12:49:45AM +0530, Kanchan Joshi wrote:
> > > OTOH, this patch implemented a software-only way out. There are some
> > > checks, but someone (either SW or HW) has to do those to keep things
> > > right.
> >
> > It only verifies it to the read/write family of commands by
> > interpreting these commands.  It still leaves a wide hole for any
> > other command.
> 
> Can you please explain for what command do you see the hole? I am
> trying to see if it is really impossible to fix this hole for good.
> 
> We only need to check for specific io commands of the NVM/ZNS command
> set that can do extra DMA.

The spec defines a few commands that may use MPTR, but most of the
possible opcodes that could use it are not defined in spec. You'd have
to break forward compatibility through this interface for non-root users
by limiting its use to only the known opcodes and reject everything
else.