[PATCH v2] drm/bridge: imx8qxp-pxl2dpi: avoid of_node_put() on ERR_PTR()

[Guangshuo Li]

imx8qxp_pxl2dpi_get_available_ep_from_port() may return ERR_PTR(-ENODEV)
or ERR_PTR(-EINVAL). imx8qxp_pxl2dpi_find_next_bridge() stores that
value in a __free(device_node) variable and then immediately checks
IS_ERR(ep).

On the error path, returning from the function triggers the cleanup
handler for __free(device_node). Since the device_node cleanup helper
only checks for NULL before calling of_node_put(), this results in
of_node_put(ERR_PTR(...)), which may lead to an invalid kobject_put()
dereference and crash the kernel.

Fix it by avoiding __free(device_node) for the endpoint pointer and
releasing it explicitly after obtaining the remote port parent.

This issue was found by a custom static analysis tool.

Fixes: ceea3f7806a10 ("drm/bridge: imx8qxp-pxl2dpi: simplify put of device_node pointers")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Guangshuo Li <lgs201920130244@xxxxxxxxx>
---
v2:
  - Fix DEFINE_FREE(device_node, ...) directly

 include/linux/of.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/of.h b/include/linux/of.h
index 2b95777f16f6..600a6e8418bb 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -135,7 +135,7 @@ static inline struct device_node *of_node_get(struct device_node *node)
 }
 static inline void of_node_put(struct device_node *node) { }
 #endif /* !CONFIG_OF_DYNAMIC */
-DEFINE_FREE(device_node, struct device_node *, if (_T) of_node_put(_T))
+DEFINE_FREE(device_node, struct device_node *, if (_T && !IS_ERR(_T)) of_node_put(_T))
 
 /* Pointer for first entry in chain of all nodes. */
 extern struct device_node *of_root;
-- 
2.43.0