[PATCH v3] PCI: fix reference leak in pci_alloc_child_bus()

[Ma Ke <make24@iscas.ac.cn>]

When device_register(&child->dev) failed, we should call put_device()
to explicitly release child->dev.

As comment of device_register() says, 'NOTE: _Never_ directly free
@dev after calling this function, even if it returned an error! Always
use put_device() to give up the reference initialized in this function
instead.'

Found by code review.

Cc: stable@vger.kernel.org
Fixes: 4f535093cf8f ("PCI: Put pci_dev in device tree as early as possible")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
Changes in v3:
- modified the description as suggestions.
Changes in v2:
- added the bug description about the comment of device_add();
- fixed the patch as suggestions;
- added Cc and Fixes table.
---
 drivers/pci/probe.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 2e81ab0f5a25..51b78fcda4eb 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1174,7 +1174,10 @@ static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent,
 add_dev:
 	pci_set_bus_msi_domain(child);
 	ret = device_register(&child->dev);
-	WARN_ON(ret < 0);
+	if (WARN_ON(ret < 0)) {
+		put_device(&child->dev);
+		return NULL;
+	}
 
 	pcibios_add_bus(child);
 
-- 
2.25.1