Re: [PATCH v2 1/7] s390/pci: Fix double-free and NULL deref in zpci MSI domain cleanup

[Niklas Schnelle <schnelle@linux.ibm.com>]

On Mon, 2026-10-05 at 14:03 +0200, Tobias Schumacher wrote:
> zpci_remove_parent_msi_domain() dereferences zbus->msi_parent_domain
> unconditionally and does not clear it afterwards.
> 
> zpci_bus_create_pci_bus() removes the domain when pci_create_root_bus()
> fails, then zpci_bus_release() removes it again on the last kref_put(),
> reading ->fwnode from the freed irq_domain and freeing it twice.
> 
> If zpci_alloc_domain() or zpci_create_parent_msi_domain() fails, no domain
> is created at all; zbus is kzalloc'd, so the same release path dereferences
> NULL.
> 
> Return early when there is no domain, and clear the pointer after removing
> one.
> 
> Fixes: f770950a4709 ("s390/pci: Migrate s390 IRQ logic to IRQ domain API")
> Cc: stable@vger.kernel.org
> Signed-off-by: Tobias Schumacher <ts@linux.ibm.com>
> ---
>  arch/s390/pci/pci_irq.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/s390/pci/pci_irq.c b/arch/s390/pci/pci_irq.c
> index 9c9ed3d8d959..c9520a16ca75 100644
> --- a/arch/s390/pci/pci_irq.c
> +++ b/arch/s390/pci/pci_irq.c
> @@ -533,9 +533,13 @@ void zpci_remove_parent_msi_domain(struct zpci_bus *zbus)
>  {
>  	struct fwnode_handle *fn;
>  
> +	if (!zbus->msi_parent_domain)
> +		return;
> +
>  	fn = zbus->msi_parent_domain->fwnode;
>  	irq_domain_remove(zbus->msi_parent_domain);
>  	irq_domain_free_fwnode(fn);
> +	zbus->msi_parent_domain = NULL;
>  }
>  
>  static void __init cpu_enable_directed_irq(void *unused)

Thanks for the fix!

Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>