| Description: | Xen 3.3.x through 4.5.x and the Linux kernel through 3.19.1 do not properly restrict access to PCI command registers, which might allow local guest OS users to cause a denial of service (non-maskable interrupt and host crash) by disabling the (1) memory or (2) I/O decoding for a PCI Express device and then accessing the device, which triggers an Unsupported Request (UR) response. Jan Beulich discovered the Xen virtual machine subsystem of the Linux kernel did not properly restrict access to PCI command registers. A local guest user could exploit this flaw to cause a denial of service (host crash).
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