[PATCH] vfio/pci: sanitize bogus INTx interrupt pin values

[Christos Longros <chris.longros@gmail.com>]

Some PCI devices report invalid interrupt pin values in config space
(e.g., 0xFF instead of the valid range 0-4).  The VFIO PCI config
virtualization layer passes these values through to userspace, causing
QEMU to crash with an assertion failure in pci_irq_handler() when it
computes irq_num = pin - 1, which exceeds PCI_NUM_PINS (4).

The existing code already handles bogus VF interrupt pins (set to 0
per SR-IOV spec §3.4.1.18), but physical functions with out-of-range
pin values are not caught.  Extend the condition that clears the
virtualized interrupt pin to also cover values outside 1-4.

Observed on Realtek RTL8852CE (10ec:c852) which reports interrupt pin
0xFF in hardware config space.

Signed-off-by: Christos Longros <chris.longros@gmail.com>
---
 drivers/vfio/pci/vfio_pci_config.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index b4e39253f..ed75c1cc3 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -1829,8 +1829,17 @@ int vfio_config_init(struct vfio_pci_core_device *vdev)
 					cpu_to_le16(PCI_COMMAND_MEMORY);
 	}
 
+	/*
+	 * Sanitize bogus interrupt pin values.  Valid pins are 1 (INTA)
+	 * through 4 (INTD); anything else disables legacy interrupts.
+	 */
+	if (vconfig[PCI_INTERRUPT_PIN] > 4)
+		pci_info(pdev, "Bogus INTx pin %d, disabling INTx virtualization\n",
+			 vconfig[PCI_INTERRUPT_PIN]);
+
 	if (!IS_ENABLED(CONFIG_VFIO_PCI_INTX) || vdev->nointx ||
-	    !vdev->pdev->irq || vdev->pdev->irq == IRQ_NOTCONNECTED)
+	    !vdev->pdev->irq || vdev->pdev->irq == IRQ_NOTCONNECTED ||
+	    vconfig[PCI_INTERRUPT_PIN] > 4)
 		vconfig[PCI_INTERRUPT_PIN] = 0;
 
 	ret = vfio_cap_init(vdev);
-- 
2.53.0