• Huang Ying's avatar
    KVM: Avoid killing userspace through guest SRAO MCE on unmapped pages · bf998156
    Huang Ying authored
    In common cases, guest SRAO MCE will cause corresponding poisoned page
    be un-mapped and SIGBUS be sent to QEMU-KVM, then QEMU-KVM will relay
    the MCE to guest OS.
    
    But it is reported that if the poisoned page is accessed in guest
    after unmapping and before MCE is relayed to guest OS, userspace will
    be killed.
    
    The reason is as follows. Because poisoned page has been un-mapped,
    guest access will cause guest exit and kvm_mmu_page_fault will be
    called. kvm_mmu_page_fault can not get the poisoned page for fault
    address, so kernel and user space MMIO processing is tried in turn. In
    user MMIO processing, poisoned page is accessed again, then userspace
    is killed by force_sig_info.
    
    To fix the bug, kvm_mmu_page_fault send HWPOISON signal to QEMU-KVM
    and do not try kernel and user space MMIO processing for poisoned
    page.
    
    [xiao: fix warning introduced by avi]
    Reported-by: default avatarMax Asbock <masbock@linux.vnet.ibm.com>
    Signed-off-by: default avatarHuang Ying <ying.huang@intel.com>
    Signed-off-by: default avatarXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
    Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
    Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
    bf998156
mmu.c 81.2 KB