Re: [PATCH] vfio/type1: Cleanup remaining vaddr removal/update fragments

Steven Sistare
2022-12-12T20:59:59Z

On 12/12/2022 10:58 AM, Alex Williamson wrote:
> On Mon, 12 Dec 2022 09:17:54 -0400
> Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
>> On Sat, Dec 10, 2022 at 09:14:06AM -0500, Steven Sistare wrote:
>>
>>> Thank you for your thoughtful response. Rather than debate the degree of
>>> of vulnerability, I propose an alternate solution. The technical crux of
>>> the matter is support for mediated devices.
>>
>> I'm not sure I'm convinced about that. It is easy to make problematic
>> situations with mdevs, but that doesn't mean other cases don't exist
>> too eg what happens if userspace suspends and then immediately does
>> something to trigger a domain attachment? Doesn't it still deadlock
>> the kernel?
>
> The opportunity for that to deadlock isn't obvious to me, a replay
> would be stalled waiting for invalid vaddrs, but this is essentially
> the user deadlocking themselves. There's also code there to handle the
> process getting killed while waiting, making it interruptible. Thanks,

I will submit new patches tomorrow to exclude mdevs. Almost done.

- Steve