CVE-2017-1000252: KVM denial of service with posted interrupts on Intel systems (since Linux 4.4)

["Jan H. Schönherr" <jschoenh () amazon de>]

Hi.

We have discovered a user triggerable BUG() when using KVM with posted interrupts on Intel
systems. This requires an unprivileged user to have access to the KVM device.

Certain values in a KVM_IRQFD API call can trigger a BUG_ON() at a later point in
vmx_update_pi_irte(). KVM as a whole seems to hang after that.

The issue was introduced with Linux 4.4, patches have been posted to the KVM
mailing list:
- https://marc.info/?l=kvm&m=150549145711115&w=2
- https://marc.info/?l=kvm&m=150549146311117&w=2

Regards
Jan H. Schönherr