From: Suravee Suthikulpanit suravee.suthikulpanit@amd.com
commit f6426ab9c957e97418ac5b0466538792767b1738 upstream.
The function amd_ir_set_vcpu_affinity makes use of the parameter struct amd_iommu_pi_data.prev_ga_tag to determine if it should delete struct amd_iommu_pi_data from a list when not running in AVIC mode.
However, prev_ga_tag is initialized only when AVIC is enabled. The non-zero uninitialized value can cause unintended code path, which ends up making use of the struct vcpu_svm.ir_list and ir_list_lock without being initialized (since they are intended only for the AVIC case).
This triggers NULL pointer dereference bug in the function vm_ir_list_del with the following call trace:
svm_update_pi_irte+0x3c2/0x550 [kvm_amd] ? proc_create_single_data+0x41/0x50 kvm_arch_irq_bypass_add_producer+0x40/0x60 [kvm] __connect+0x5f/0xb0 [irqbypass] irq_bypass_register_producer+0xf8/0x120 [irqbypass] vfio_msi_set_vector_signal+0x1de/0x2d0 [vfio_pci] vfio_msi_set_block+0x77/0xe0 [vfio_pci] vfio_pci_set_msi_trigger+0x25c/0x2f0 [vfio_pci] vfio_pci_set_irqs_ioctl+0x88/0xb0 [vfio_pci] vfio_pci_ioctl+0x2ea/0xed0 [vfio_pci] ? alloc_file_pseudo+0xa5/0x100 vfio_device_fops_unl_ioctl+0x26/0x30 [vfio] ? vfio_device_fops_unl_ioctl+0x26/0x30 [vfio] __x64_sys_ioctl+0x96/0xd0 do_syscall_64+0x37/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Therefore, initialize prev_ga_tag to zero before use. This should be safe because ga_tag value 0 is invalid (see function avic_vm_init).
Fixes: dfa20099e26e ("KVM: SVM: Refactor AVIC vcpu initialization into avic_init_vcpu()") Signed-off-by: Suravee Suthikulpanit suravee.suthikulpanit@amd.com Message-Id: 20201003232707.4662-1-suravee.suthikulpanit@amd.com Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/svm.c | 1 + 1 file changed, 1 insertion(+)
--- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -5380,6 +5380,7 @@ static int svm_update_pi_irte(struct kvm * - Tell IOMMU to use legacy mode for this interrupt. * - Retrieve ga_tag of prior interrupt remapping data. */ + pi.prev_ga_tag = 0; pi.is_guest_mode = false; ret = irq_set_vcpu_affinity(host_irq, &pi);