[PATCH v2] ocxl: fix pci device refcount leak when calling get_function_0()

[Yang Yingliang]

get_function_0() calls pci_get_domain_bus_and_slot(), as comment
says, it returns a pci device with refcount increment, so after
using it, pci_dev_put() needs be called.

Get the device reference when get_function_0() is not called, so
pci_dev_put() can be called in the error path and callers
unconditionally. And add comment above get_dvsec_vendor0() to tell
callers to call pci_dev_put().

Fixes: 87db7579ebd5 ("ocxl: control via sysfs whether the FPGA is reloaded on a 
link reset")
Suggested-by: Andrew Donnellan <a...@linux.ibm.com>
Signed-off-by: Yang Yingliang <yangyingli...@huawei.com>
---
v1 -> v2:
  Add comment above get_dvsec_vendor0().
  Get reference where dev is function 0, and call pci_dev_put()
  unconditionally in callers.
---
 drivers/misc/ocxl/config.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/ocxl/config.c b/drivers/misc/ocxl/config.c
index e401a51596b9..92ab49705f64 100644
--- a/drivers/misc/ocxl/config.c
+++ b/drivers/misc/ocxl/config.c
@@ -193,6 +193,18 @@ static int read_dvsec_vendor(struct pci_dev *dev)
        return 0;
 }
 
+/**
+ * get_dvsec_vendor0() - Find a related PCI device (function 0)
+ * @dev: PCI device to match
+ * @dev0: The PCI device (function 0) found
+ * @out_pos: The position of PCI device (function 0)
+ *
+ * Returns 0 on success, negative on failure.
+ *
+ * NOTE: If it's successful, the reference of dev0 is increased,
+ * so after using it, the callers must call pci_dev_put() to give
+ * up the reference.
+ */
 static int get_dvsec_vendor0(struct pci_dev *dev, struct pci_dev **dev0,
                             int *out_pos)
 {
@@ -202,10 +214,14 @@ static int get_dvsec_vendor0(struct pci_dev *dev, struct 
pci_dev **dev0,
                dev = get_function_0(dev);
                if (!dev)
                        return -1;
+       } else {
+               dev = pci_dev_get(dev);
        }
        pos = find_dvsec(dev, OCXL_DVSEC_VENDOR_ID);
-       if (!pos)
+       if (!pos) {
+               pci_dev_put(dev);
                return -1;
+       }
        *dev0 = dev;
        *out_pos = pos;
        return 0;
@@ -222,6 +238,7 @@ int ocxl_config_get_reset_reload(struct pci_dev *dev, int 
*val)
 
        pci_read_config_dword(dev0, pos + OCXL_DVSEC_VENDOR_RESET_RELOAD,
                              &reset_reload);
+       pci_dev_put(dev0);
        *val = !!(reset_reload & BIT(0));
        return 0;
 }
@@ -243,6 +260,7 @@ int ocxl_config_set_reset_reload(struct pci_dev *dev, int 
val)
                reset_reload &= ~BIT(0);
        pci_write_config_dword(dev0, pos + OCXL_DVSEC_VENDOR_RESET_RELOAD,
                               reset_reload);
+       pci_dev_put(dev0);
        return 0;
 }
 
-- 
2.25.1