Re: [PATCH 1/2] i2c: virtio: disable timeout handling

[Jie Deng]

On 2021/10/20 19:03, Viresh Kumar wrote:
> On 20-10-21, 12:55, Vincent Whitchurch wrote:
> > If the timeout cannot be disabled, then the driver should be fixed to
> > always copy buffers and hold on to them to avoid memory corruption in
> > the case of timeout, as I mentioned in my commit message.  That would be
> > quite a substantial change to the driver so it's not something I'm
> > personally comfortable with doing, especially not this late in the -rc
> > cycle, so I'd leave that to others.
> Or we can avoid clearing up and freeing the buffers here until the
> point where the buffers are returned by the host. Until that happens,
> we can avoid taking new requests but return to the earlier caller with
> timeout failure. That would avoid corruption, by freeing buffers
> sooner, and not hanging of the kernel.


It seems similar to use "wait_for_completion". If the other side is 
hacked, the guest may never

get the buffers returned by the host, right ?


For this moment, we can solve the problem by using a hardcoded big value 
or disabling the timeout.

Over the long term, I think the backend should provide that timeout 
value and guarantee that its processing

time should not exceed that value.