[PATCH] bus: arm-cci: fix device_node refcount leak in cci_probe_ports()

[Manush Prajwal]

cci_probe_ports() has two device_node refcount bugs in its
for_each_available_child_of_node() loop over "cp":

 - When the computed port index "i" reaches nb_cci_ports, the loop
   breaks out without releasing the reference the iterator was
   holding on "cp", leaking it.

 - When a port is successfully parsed, "cp" is stored into
   ports[i].dn for later use, but the loop keeps iterating afterwards.
   The next for_each_available_child_of_node() step puts the
   reference on the previous "cp" to advance to the next sibling, so
   the pointer saved in ports[i].dn is left referencing a node whose
   reference was already dropped.

Rework the loop around for_each_available_child_of_node_scoped()
so the iterator's reference is dropped automatically on every exit
path, including the early break. Since a matched node is kept alive
in ports[i].dn past the end of the loop, take an explicit reference
with of_node_get() when storing it.

Signed-off-by: Manush Prajwal <manushprajwal555 at gmail.com>
---
 drivers/bus/arm-cci.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
index 000000000..000000000 100644
--- a/drivers/bus/arm-cci.c
+++ b/drivers/bus/arm-cci.c
@@ -438,8 +438,7 @@
 static int cci_probe_ports(struct device_node *np)
 {
 	struct cci_nb_ports const *cci_config;
 	int ret, i, nb_ace = 0, nb_ace_lite = 0;
-	struct device_node *cp;
 	struct resource res;
 	const char *match_str;
 	bool is_ace;
@@ -455,7 +455,7 @@ static int cci_probe_ports(struct device_node *np)
 	if (!ports)
 		return -ENOMEM;

-	for_each_available_child_of_node(np, cp) {
+	for_each_available_child_of_node_scoped(np, cp) {
 		if (!of_match_node(arm_cci_ctrl_if_matches, cp))
 			continue;

@@ -498,7 +498,7 @@ static int cci_probe_ports(struct device_node *np)
 			ports[i].type = ACE_LITE_PORT;
 			++nb_ace_lite;
 		}
-		ports[i].dn = cp;
+		ports[i].dn = of_node_get(cp);
 	}

 	/*
--
2.46.2.windows.1