[PATCH] 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.

Store the callback result, release the reference after callback dispatch,
and then return the result. This keeps the device alive while its callback
runs and balances the lookup on every successful path.

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

Fixes: 956a9202cd12 ("xen-pcifront: Xen PCI frontend driver.")
Signed-off-by: Ruoyu Wang <ruoyuw560@gmail.com>
---
 drivers/pci/xen-pcifront.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index cffc32d6603277..07263dfe22d538 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -575,6 +575,7 @@ static pci_ers_result_t pcifront_common_process(int cmd,
 						struct pcifront_device *pdev,
 						pci_channel_state_t state)
 {
+	pci_ers_result_t result = PCI_ERS_RESULT_NONE;
 	struct pci_driver *pdrv;
 	int bus = pdev->sh_info->aer_op.bus;
 	int devfn = pdev->sh_info->aer_op.devfn;
@@ -597,21 +598,25 @@ static pci_ers_result_t pcifront_common_process(int cmd,
 		pci_dbg(pcidev, "trying to call AER service\n");
 		switch (cmd) {
 		case XEN_PCI_OP_aer_detected:
-			return pdrv->err_handler->error_detected(pcidev, state);
+			result = pdrv->err_handler->error_detected(pcidev, state);
+			break;
 		case XEN_PCI_OP_aer_mmio:
-			return pdrv->err_handler->mmio_enabled(pcidev);
+			result = pdrv->err_handler->mmio_enabled(pcidev);
+			break;
 		case XEN_PCI_OP_aer_slotreset:
-			return pdrv->err_handler->slot_reset(pcidev);
+			result = pdrv->err_handler->slot_reset(pcidev);
+			break;
 		case XEN_PCI_OP_aer_resume:
 			pdrv->err_handler->resume(pcidev);
-			return PCI_ERS_RESULT_NONE;
+			break;
 		default:
 			dev_err(&pdev->xdev->dev,
 				"bad request in aer recovery operation!\n");
 		}
 	}
 
-	return PCI_ERS_RESULT_NONE;
+	pci_dev_put(pcidev);
+	return result;
 }
 
 
-- 
2.51.0