[PATCH] xen-pciback: Fix pcistub_device ref leak in pcistub_get_gsi_from_sbdf()

[Wentao Liang <vulab@xxxxxxxxxxx>]

pcistub_get_gsi_from_sbdf() obtains the stub device with
pcistub_device_find(), which returns it with its kref incremented, and
returns psdev->gsi without dropping that reference again.  The caller
cannot release it either, so every lookup leaks one reference to the
stub device.

Release the reference after reading gsi.

Fixes: 2fae6bb7be32 ("xen/privcmd: Add new syscall to get gsi from dev")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Wentao Liang <vulab@xxxxxxxxxxx>
---
 drivers/xen/xen-pciback/pci_stub.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/xen-pciback/pci_stub.c 
b/drivers/xen/xen-pciback/pci_stub.c
index 79a2b5dfd694..d1a335233aab 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -234,13 +234,16 @@ static int pcistub_get_gsi_from_sbdf(unsigned int sbdf)
        int bus = PCI_BUS_NUM(sbdf);
        int slot = PCI_SLOT(sbdf);
        int func = PCI_FUNC(sbdf);
+       int gsi;
 
        psdev = pcistub_device_find(domain, bus, slot, func);
-
        if (!psdev)
                return -ENODEV;
 
-       return psdev->gsi;
+       gsi = psdev->gsi;
+       pcistub_device_put(psdev);
+
+       return gsi;
 }
 #endif
 
-- 
2.34.1