Re: [Qemu-devel] [PATCH v1 1/1] cadence_uart: Check baud rate generator and divider values on migration

[Alistair Francis <alistair.francis@xilinx.com>]

On Mon, Nov 7, 2016 at 2:13 PM, Peter Maydell <peter.maydell@linaro.org> wrote:
> On 7 November 2016 at 21:53, Alistair Francis
> <alistair.francis@xilinx.com> wrote:
>> On Sat, Nov 5, 2016 at 6:51 AM, Peter Maydell <peter.maydell@linaro.org> wrote:
>>> Usually we just fail the migration if the incoming
>>> data is bogus -- any particular reason not to take that
>>> approach here?
>>
>> There is no reason, it just seemed a bit much to abort just for this.
>>
>> Should I change it to abort?
>
> I think there are two cases:
>  (1) migration from an old version could be in these
> bogus states (without having crashed the old version
> in the process) -- in that case you can argue for
> sanitizing as being most helpful to the user
> (and should comment that that's why we accept-but-squash)

I think this is actually very unlikely, anyone setting these values by
accident has probably already seen crashes.

>  (2) the out-of-bounds values only happen if somebody
> is deliberately feeding QEMU a bogus incoming data
> stream -- in this case (which is the usual one for
> bounds checks) it's best to return 1 to fail the
> migration.

This seems more likely, so it sounds like I should fail the migration.

Thanks,

Alistair

>
> thanks
> -- PMM
>