Re: [PATCH] KVM: SVM: fix panic on out-of-bounds guest IRQ

[Paolo Bonzini <pbonzini@redhat.com>]

On 3/9/22 12:30, Yi Wang wrote:
> As guest_irq is coming from KVM_IRQFD API call, it may trigger
> crash in svm_update_pi_irte() due to out-of-bounds:
> 
> crash> bt
> PID: 22218  TASK: ffff951a6ad74980  CPU: 73  COMMAND: "vcpu8"
>   #0 [ffffb1ba6707fa40] machine_kexec at ffffffff8565b397
>   #1 [ffffb1ba6707fa90] __crash_kexec at ffffffff85788a6d
>   #2 [ffffb1ba6707fb58] crash_kexec at ffffffff8578995d
>   #3 [ffffb1ba6707fb70] oops_end at ffffffff85623c0d
>   #4 [ffffb1ba6707fb90] no_context at ffffffff856692c9
>   #5 [ffffb1ba6707fbf8] exc_page_fault at ffffffff85f95b51
>   #6 [ffffb1ba6707fc50] asm_exc_page_fault at ffffffff86000ace
>      [exception RIP: svm_update_pi_irte+227]
>      RIP: ffffffffc0761b53  RSP: ffffb1ba6707fd08  RFLAGS: 00010086
>      RAX: ffffb1ba6707fd78  RBX: ffffb1ba66d91000  RCX: 0000000000000001
>      RDX: 00003c803f63f1c0  RSI: 000000000000019a  RDI: ffffb1ba66db2ab8
>      RBP: 000000000000019a   R8: 0000000000000040   R9: ffff94ca41b82200
>      R10: ffffffffffffffcf  R11: 0000000000000001  R12: 0000000000000001
>      R13: 0000000000000001  R14: ffffffffffffffcf  R15: 000000000000005f
>      ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
>   #7 [ffffb1ba6707fdb8] kvm_irq_routing_update at ffffffffc09f19a1 [kvm]
>   #8 [ffffb1ba6707fde0] kvm_set_irq_routing at ffffffffc09f2133 [kvm]
>   #9 [ffffb1ba6707fe18] kvm_vm_ioctl at ffffffffc09ef544 [kvm]
> #10 [ffffb1ba6707ff10] __x64_sys_ioctl at ffffffff85935474
> #11 [ffffb1ba6707ff40] do_syscall_64 at ffffffff85f921d3
> #12 [ffffb1ba6707ff50] entry_SYSCALL_64_after_hwframe at ffffffff8600007c
>      RIP: 00007f143c36488b  RSP: 00007f143a4e04b8  RFLAGS: 00000246
>      RAX: ffffffffffffffda  RBX: 00007f05780041d0  RCX: 00007f143c36488b
>      RDX: 00007f05780041d0  RSI: 000000004008ae6a  RDI: 0000000000000020
>      RBP: 00000000000004e8   R8: 0000000000000008   R9: 00007f05780041e0
>      R10: 00007f0578004560  R11: 0000000000000246  R12: 00000000000004e0
>      R13: 000000000000001a  R14: 00007f1424001c60  R15: 00007f0578003bc0
>      ORIG_RAX: 0000000000000010  CS: 0033  SS: 002b
> 
> Vmx have been fix this in commit 3a8b0677fc61 (KVM: VMX: Do not BUG() on
> out-of-bounds guest IRQ), so we can just copy source from that to fix
> this.
> 
> Signed-off-by: Yi Wang <wang.yi59@zte.com.cn>
> Signed-off-by: Yi Liu <liu.yi24@zte.com.cn>

Hi, the Signed-off-by chain is wrong.  Did Yi Liu write the patch (and 
you are just sending it)?

Paolo

> ---
>   arch/x86/kvm/svm/avic.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index fb3e20791338..f59b93d8e95a 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -783,7 +783,7 @@ int svm_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
>   {
>   	struct kvm_kernel_irq_routing_entry *e;
>   	struct kvm_irq_routing_table *irq_rt;
> -	int idx, ret = -EINVAL;
> +	int idx, ret = 0;
>   
>   	if (!kvm_arch_has_assigned_device(kvm) ||
>   	    !irq_remapping_cap(IRQ_POSTING_CAP))
> @@ -794,7 +794,13 @@ int svm_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
>   
>   	idx = srcu_read_lock(&kvm->irq_srcu);
>   	irq_rt = srcu_dereference(kvm->irq_routing, &kvm->irq_srcu);
> -	WARN_ON(guest_irq >= irq_rt->nr_rt_entries);
> +
> +	if (guest_irq >= irq_rt->nr_rt_entries ||
> +		hlist_empty(&irq_rt->map[guest_irq])) {
> +		pr_warn_once("no route for guest_irq %u/%u (broken user space?)\n",
> +			     guest_irq, irq_rt->nr_rt_entries);
> +		goto out;
> +	}
>   
>   	hlist_for_each_entry(e, &irq_rt->map[guest_irq], link) {
>   		struct vcpu_data vcpu_info;