[PATCH 1/7] s390/pci: fix double-free in zpci MSI cleanup

zpci_remove_parent_msi_domain() can be called multiple times on the
same zbus, causing a double-free. This occurs when pci_create_root_bus()
fails after successful MSI domain creation in zpci_bus_create_pci_bus():
the error path calls zpci_remove_parent_msi_domain() to clean up, but
doesn't NULL the pointer. Later, when zpci_bus_release() is called via
kref_put(), it calls zpci_remove_parent_msi_domain() again, attempting
to free the already-freed domain and fwnode.

Add NULL check at function entry and NULL the pointer after cleanup to
make the function idempotent and safe for multiple calls.

Fixes: f770950a4709 ("s390/pci: Migrate s390 IRQ logic to IRQ domain API")
Cc: [email protected]
Signed-off-by: Tobias Schumacher <[email protected]>
---
 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)

-- 
2.53.0