Re: [PATCH v3] arm/ioreq: guard interaction data on read/write operations

[Julien Grall <julien@xxxxxxx>]

On 05/10/2023 16:17, Julien Grall wrote:
> Hi Andrii,
Hi,

> On 05/10/2023 14:30, Andrii Chepurnyi wrote:
> > For read operations, there's a potential issue when the data field
> > of the ioreq struct is partially updated in the response. To address
> > this, zero data field during read operations. This modification
> > serves as a safeguard against implementations that may inadvertently
> > partially update the data field in response to read requests.
> > For instance, consider an 8-bit read operation. In such cases, QEMU,
> > returns the same content of the data field with only 8 bits of
> > updated data. This behavior could potentially result in the
> > propagation of incorrect or unintended data to ioreq clients.
> > During a write access, the Device Model only need to know the content
> > of the bits associated with the access size (e.g. for 8-bit, the lower
> > 8-bits). During a read access, the Device Model don't need to know any
> > value. So restrict the value it can access.
> >
> > Signed-off-by: Andrii Chepurnyi <andrii_chepurnyi@xxxxxxxx>
> Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
>
> Unless there are any objections, I will commit the patch tomorrow (Friday).
And now committed. Thanks!

I am not sure I would consider it for backport because the IOREQ is 
still a tech preview on Arm. We should consider to switch to SUPPORT, 
that said there is at least one bug that would need to be fixed first [1].
Cheers,

[1] 20201005140817.1339-1-paul@xxxxxxx

--
Julien Grall