On Wed, 13 May 2020 09:26:30 -0400
Pan Nengyuan <pannengyuan@xxxxxxxxxx> wrote:
> When we hotplug vcpus, cpu_update_state is added to vm_change_state_head
> in kvm_arch_init_vcpu(). But it forgot to delete in kvm_arch_destroy_vcpu() after
> unplug. Then it will cause a use-after-free access. This patch delete it in
> kvm_arch_destroy_vcpu() to fix that.
>
> Reproducer:
> virsh setvcpus vm1 4 --live
> virsh setvcpus vm1 2 --live
> virsh suspend vm1
> virsh resume vm1
>
> The UAF stack:
> ==qemu-system-x86_64==28233==ERROR: AddressSanitizer: heap-use-after-free on address 0x62e00002e798 at pc 0x5573c6917d9e bp 0x7fff07139e50 sp 0x7fff07139e40
> WRITE of size 1 at 0x62e00002e798 thread T0
> #0 0x5573c6917d9d in cpu_update_state /mnt/sdb/qemu/target/i386/kvm.c:742
> #1 0x5573c699121a in vm_state_notify /mnt/sdb/qemu/vl.c:1290
> #2 0x5573c636287e in vm_prepare_start /mnt/sdb/qemu/cpus.c:2144
> #3 0x5573c6362927 in vm_start /mnt/sdb/qemu/cpus.c:2150
> #4 0x5573c71e8304 in qmp_cont /mnt/sdb/qemu/monitor/qmp-cmds.c:173
> #5 0x5573c727cb1e in qmp_marshal_cont qapi/qapi-commands-misc.c:835
> #6 0x5573c7694c7a in do_qmp_dispatch /mnt/sdb/qemu/qapi/qmp-dispatch.c:132
> #7 0x5573c7694c7a in qmp_dispatch /mnt/sdb/qemu/qapi/qmp-dispatch.c:175
> #8 0x5573c71d9110 in monitor_qmp_dispatch /mnt/sdb/qemu/monitor/qmp.c:145
> #9 0x5573c71dad4f in monitor_qmp_bh_dispatcher /mnt/sdb/qemu/monitor/qmp.c:234
>
> Reported-by: Euler Robot <euler.robot@xxxxxxxxxx>
> Signed-off-by: Pan Nengyuan <pannengyuan@xxxxxxxxxx>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
Reviewed-by: Igor Mammedov <imammedo@xxxxxxxxxx>
> ---
> - v2: remove unnecessary set vmsentry to null(there is no non-null check).
> ---
> target/i386/cpu.h | 1 +
> target/i386/kvm.c | 4 +++-
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index e818fc712a..afbd11b7a3 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -1631,6 +1631,7 @@ struct X86CPU {
>
> CPUNegativeOffsetState neg;
> CPUX86State env;
> + VMChangeStateEntry *vmsentry;
>
> uint64_t ucode_rev;
>
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index 4901c6dd74..0a4eca5a85 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -1770,7 +1770,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
> }
> }
>
> - qemu_add_vm_change_state_handler(cpu_update_state, env);
> + cpu->vmsentry = qemu_add_vm_change_state_handler(cpu_update_state, env);
>
> c = cpuid_find_entry(&cpuid_data.cpuid, 1, 0);
> if (c) {
> @@ -1883,6 +1883,8 @@ int kvm_arch_destroy_vcpu(CPUState *cs)
> env->nested_state = NULL;
> }
>
> + qemu_del_vm_change_state_handler(cpu->vmsentry);
> +
> return 0;
> }
>
