Re: [PATCH] KVM: s390: pci: Fix GISC refcount leak on AIF enable failure

[Matthew Rosato]

On 6/23/26 3:52 AM, Haoxiang Li wrote:
> kvm_s390_gisc_register() registers the guest ISC before pinning
> the guest interrupt forwarding pages and allocating the AISB bit.
> If any of the later setup steps fails, the function unwinds the
> pinned pages and other local state, but does not unregister the
> GISC reference. Add the missing kvm_s390_gisc_unregister() to the
> error unwind path.

Hi Haoxiang,

Thanks for the fix!  A comment below..

> 
> Fixes: 3c5a1b6f0a18 ("KVM: s390: pci: provide routines for enabling/disabling interrupt forwarding")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Haoxiang Li <haoxiang_li2024@xxxxxxx>
> ---
>  arch/s390/kvm/pci.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
> index 5b075c38998e..a9d5996590e7 100644
> --- a/arch/s390/kvm/pci.c
> +++ b/arch/s390/kvm/pci.c
> @@ -252,7 +252,7 @@ static int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib,
>  	srcu_read_unlock(&kvm->srcu, idx);
>  	if (npages < 1) {
>  		rc = -EIO;
> -		goto out;
> +		goto out_unregister_gisc;
>  	}
>  	aibv_page = pages[0];
>  	pcount++;
> @@ -327,6 +327,8 @@ static int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib,
>  		unpin_user_page(aisb_page);
>  unpin1:
>  	unpin_user_page(aibv_page);
> +out_unregister_gisc:
> +	kvm_s390_gisc_unregister(kvm, fib->fmt0.isc);
>  out:

Label 'out' is now unused in this function.

I think you could make this a 1-liner fix by keeping the goto unchanged
and instead just placing the unregister call right after out:

Thanks,
Matt 

>  	return rc;
>  }