Re: [PATCH] vhost/migration: Fix incorrect size used in inflight->addr in VMSD

[Peter Xu <peterx@redhat.com>]

On Wed, Jul 29, 2026 at 02:57:57PM -0400, Michael S. Tsirkin wrote:
> On Wed, Jul 29, 2026 at 01:48:25PM -0400, Peter Xu wrote:
> > So to me, it's much simpler we say migration stream must be
> > trusted, and I expect dest QEMU can allocate any buffer it needs, until it
> > eats the whole system memory.  I really don't see much real risk..
> 
> It's not risk due to migration, specifically. But making qemu
> drink up terabytes from the guest would be problematic, right?
> 
> Putting qemu in a cgroup with restricted total memory
> would be one way to prevent this class of security issue,
> and a robust one.
> 
> But that, in turn, is impossible if qemu insists on allocating
> unlimited memory at the drop of a hat.

Just to clarify at least one thing.. we have two attack surfaces here and
they're very different IMHO:

(1) guest behavior caused memory allocation, or,

(2) migration stream caused memory allocation.

AFAIU, (1) is more severe. All my points only apply to (2).

> 
> However, migration is hardly the worst offender here, and I am
> not at all sure we need to start with it if we even want
> to address this limitation.

Agree.

Thanks,

-- 
Peter Xu