FreeBSD : xen-kernel -- vulnerability in the iret hypercall handler (8c31b288-27ec-11e5-a4a5-002590263bf5)
Medium Nessus Plugin ID 84709
SynopsisThe remote FreeBSD host is missing a security-related update.
DescriptionThe Xen Project reports :
A buggy loop in Xen's compat_iret() function iterates the wrong way around a 32-bit index. Any 32-bit PV guest kernel can trigger this vulnerability by attempting a hypercall_iret with EFLAGS.VM set.
Given the use of __get/put_user(), and that the virtual addresses in question are contained within the lower canonical half, the guest cannot clobber any hypervisor data. Instead, Xen will take up to 2^33 pagefaults, in sequence, effectively hanging the host.
Malicious guest administrators can cause a denial of service affecting the whole system.
SolutionUpdate the affected package.