From 2a6931425890a9a2822e62f60724a9edbb93ba10 Mon Sep 17 00:00:00 2001 From: Pan Nengyuan Date: Wed, 13 May 2020 09:26:30 -0400 Subject: [PATCH] i386/kvm: fix a use-after-free when vcpu plug/unplug MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Pan Nengyuan Reviewed-by: Philippe Mathieu-Daudé Message-Id: <20200513132630.13412-1-pannengyuan@huawei.com> Reviewed-by: Igor Mammedov Signed-off-by: Paolo Bonzini --- 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 00d1f4f013..37572bd437 100644 --- a/target/i386/cpu.h +++ b/target/i386/cpu.h @@ -1634,6 +1634,7 @@ 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 95bbeb424b..ef2e0a81dd 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -1741,7 +1741,7 @@ 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) { @@ -1852,6 +1852,8 @@ int kvm_arch_destroy_vcpu(CPUState *cs) env->nested_state = NULL; } + qemu_del_vm_change_state_handler(cpu->vmsentry); + return 0; } -- 2.11.0