[PATCH v2] xen/pcifront: Fix PCI device reference leak in AER handling

[Ruoyu Wang <ruoyuw560@gmail.com>]

pci_get_domain_bus_and_slot() increments the reference count of the
returned PCI device. pcifront_common_process() drops that reference only
when the device or its driver is missing. All paths for a bound device
either return directly after invoking an error recovery callback or fall
through without calling pci_dev_put(). Consequently, each AER request for
a bound device leaks a reference and can keep the device allocated after
removal.

Declare the looked-up device with __free(pci_dev_put), so every return
path releases the reference after callback dispatch. This keeps the
device alive while its callback runs and balances the lookup without
restructuring the callback returns.

This issue was found by a static analysis checker and confirmed by manual
source review.

Fixes: 956a9202cd12 ("xen-pcifront: Xen PCI frontend driver.")
Suggested-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Ruoyu Wang <ruoyuw560@gmail.com>
---
Changes in v2:
- Use __free(pci_dev_put) instead of restructuring the callback returns.

Link: https://lore.kernel.org/r/20260813153138.3953222-1-ruoyuw560@gmail.com/
---
 drivers/pci/xen-pcifront.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index cffc32d660327..0dea8a69fa36c 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -579,16 +579,15 @@ static pci_ers_result_t pcifront_common_process(int cmd,
 	int bus = pdev->sh_info->aer_op.bus;
 	int devfn = pdev->sh_info->aer_op.devfn;
 	int domain = pdev->sh_info->aer_op.domain;
-	struct pci_dev *pcidev;
+	struct pci_dev *pcidev __free(pci_dev_put) =
+		pci_get_domain_bus_and_slot(domain, bus, devfn);
 
 	dev_dbg(&pdev->xdev->dev,
 		"pcifront AER process: cmd %x (bus:%x, devfn%x)",
 		cmd, bus, devfn);
 
-	pcidev = pci_get_domain_bus_and_slot(domain, bus, devfn);
 	if (!pcidev || !pcidev->dev.driver) {
 		dev_err(&pdev->xdev->dev, "device or AER driver is NULL\n");
-		pci_dev_put(pcidev);
 		return PCI_ERS_RESULT_NONE;
 	}
 	pdrv = to_pci_driver(pcidev->dev.driver);
-- 
2.51.0