i386/kvm: fix a use-after-free when vcpu plug/unplug
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@huawei.com> Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> Message-Id: <20200513132630.13412-1-pannengyuan@huawei.com> Reviewed-by: Igor Mammedov <imammedo@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@ -1634,6 +1634,7 @@ struct X86CPU {
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CPUNegativeOffsetState neg;
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CPUX86State env;
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VMChangeStateEntry *vmsentry;
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uint64_t ucode_rev;
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@ -1741,7 +1741,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
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}
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}
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qemu_add_vm_change_state_handler(cpu_update_state, env);
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cpu->vmsentry = qemu_add_vm_change_state_handler(cpu_update_state, env);
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c = cpuid_find_entry(&cpuid_data.cpuid, 1, 0);
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if (c) {
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@ -1852,6 +1852,8 @@ int kvm_arch_destroy_vcpu(CPUState *cs)
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env->nested_state = NULL;
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}
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qemu_del_vm_change_state_handler(cpu->vmsentry);
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return 0;
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}
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