Re: CVE-2021-47575: xen/console: harden hvc_xen against event channel storms

Re: CVE-2021-47575: xen/console: harden hvc_xen against event channel storms

[Juergen Gross]

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On 19.06.24 16:54, Greg Kroah-Hartman wrote:
> Description
> ===========
> 
> In the Linux kernel, the following vulnerability has been resolved:
> 
> xen/console: harden hvc_xen against event channel storms
> 
> The Xen console driver is still vulnerable for an attack via excessive
> number of events sent by the backend. Fix that by using a lateeoi event
> channel.
> 
> For the normal domU initial console this requires the introduction of
> bind_evtchn_to_irq_lateeoi() as there is no xenbus device available
> at the time the event channel is bound to the irq.
> 
> As the decision whether an interrupt was spurious or not requires to
> test for bytes having been read from the backend, move sending the
> event into the if statement, as sending an event without having found
> any bytes to be read is making no sense at all.
> 
> This is part of XSA-391

When issuing XSA-391 the Xen security team already assigned CVE-2021-28713
to this issue.


Juergen

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