[PATCH AUTOSEL 4.18 075/126] net: stmmac: dwmac-sun8i: fix OF child-node lookup

From: Sasha Levin
Date: Wed Oct 31 2018 - 19:34:45 EST

From: Johan Hovold <johan@xxxxxxxxxx>

[ Upstream commit ac63043d8cb5503c7e0fe110f947eacf2663804e ]

Use the new of_get_compatible_child() helper to lookup the mdio-internal
child node instead of using of_find_compatible_node(), which searches
the entire tree from a given start node and thus can return an unrelated
(i.e. non-child) node.

This also addresses a potential use-after-free (e.g. after probe
deferral) as the tree-wide helper drops a reference to its first
argument (i.e. the mdio-mux node). Fortunately, this was inadvertently
balanced by a failure to drop the mdio-mux reference after lookup.

While at it, also fix the related mdio-internal- and phy-node reference

Fixes: 634db83b8265 ("net: stmmac: dwmac-sun8i: Handle integrated/external MDIOs")
Tested-by: Corentin Labbe <clabbe.montjoie@xxxxxxxxx>
Cc: Andrew Lunn <andrew@xxxxxxx>
Cc: Giuseppe Cavallaro <peppe.cavallaro@xxxxxx>
Cc: Alexandre Torgue <alexandre.torgue@xxxxxx>
Cc: Jose Abreu <joabreu@xxxxxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
index f9a61f90cfbc..0f660af01a4b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
@@ -714,8 +714,9 @@ static int get_ephy_nodes(struct stmmac_priv *priv)
return -ENODEV;

- mdio_internal = of_find_compatible_node(mdio_mux, NULL,
+ mdio_internal = of_get_compatible_child(mdio_mux,
+ of_node_put(mdio_mux);
if (!mdio_internal) {
dev_err(priv->device, "Cannot get internal_mdio node\n");
return -ENODEV;
@@ -729,13 +730,20 @@ static int get_ephy_nodes(struct stmmac_priv *priv)
gmac->rst_ephy = of_reset_control_get_exclusive(iphynode, NULL);
if (IS_ERR(gmac->rst_ephy)) {
ret = PTR_ERR(gmac->rst_ephy);
- if (ret == -EPROBE_DEFER)
+ if (ret == -EPROBE_DEFER) {
+ of_node_put(iphynode);
+ of_node_put(mdio_internal);
return ret;
+ }
dev_info(priv->device, "Found internal PHY node\n");
+ of_node_put(iphynode);
+ of_node_put(mdio_internal);
return 0;
+ of_node_put(mdio_internal);
return -ENODEV;