From: Paolo Bonzini pbonzini@redhat.com
commit 5593473a1e6c743764b08e3b6071cb43b5cfa6c4 upstream.
kvm_vcpu_release() will call kvm_dirty_ring_free(), freeing ring->dirty_gfns and setting it to NULL. Afterwards, it calls kvm_arch_vcpu_destroy().
However, if closing the file descriptor races with KVM_RUN in such away that vcpu->arch.st.preempted == 0, the following call stack leads to a NULL pointer dereference in kvm_dirty_run_push():
mark_page_dirty_in_slot+0x192/0x270 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3171 kvm_steal_time_set_preempted arch/x86/kvm/x86.c:4600 [inline] kvm_arch_vcpu_put+0x34e/0x5b0 arch/x86/kvm/x86.c:4618 vcpu_put+0x1b/0x70 arch/x86/kvm/../../../virt/kvm/kvm_main.c:211 vmx_free_vcpu+0xcb/0x130 arch/x86/kvm/vmx/vmx.c:6985 kvm_arch_vcpu_destroy+0x76/0x290 arch/x86/kvm/x86.c:11219 kvm_vcpu_destroy arch/x86/kvm/../../../virt/kvm/kvm_main.c:441 [inline]
The fix is to release the dirty page ring after kvm_arch_vcpu_destroy has run.
Reported-by: Qiuhao Li qiuhao@sysec.org Reported-by: Gaoning Pan pgn@zju.edu.cn Reported-by: Yongkang Jia kangel@zju.edu.cn Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- virt/kvm/kvm_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -431,8 +431,8 @@ static void kvm_vcpu_init(struct kvm_vcp
void kvm_vcpu_destroy(struct kvm_vcpu *vcpu) { - kvm_dirty_ring_free(&vcpu->dirty_ring); kvm_arch_vcpu_destroy(vcpu); + kvm_dirty_ring_free(&vcpu->dirty_ring);
/* * No need for rcu_read_lock as VCPU_RUN is the only place that changes