From ed5d2937a6a8f12e7f815748f991990e79ac4cd1 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Tue, 17 Aug 2021 17:52:45 +0300 Subject: [PATCH] net: dsa: sja1105: fix use-after-free after calling of_find_compatible_node, or worse It seems that of_find_compatible_node has a weird calling convention in which it calls of_node_put() on the "from" node argument, instead of leaving that up to the caller. This comes from the fact that of_find_compatible_node with a non-NULL "from" argument it only supposed to be used as the iterator function of for_each_compatible_node(). OF iterator functions call of_node_get on the next OF node and of_node_put() on the previous one. When of_find_compatible_node calls of_node_put, it actually never expects the refcount to drop to zero, because the call is done under the atomic devtree_lock context, and when the refcount drops to zero it triggers a kobject and a sysfs file deletion, which assume blocking context. So any driver call to of_find_compatible_node is probably buggy because an unexpected of_node_put() takes place. What should be done is to use the of_get_compatible_child() function. Fixes: 5a8f09748ee7 ("net: dsa: sja1105: register the MDIO buses for 100base-T1 and 100base-TX") Link: https://lore.kernel.org/netdev/20210814010139.kzryimmp4rizlznt@skbuf/ Suggested-by: Frank Rowand Suggested-by: Rob Herring Signed-off-by: Vladimir Oltean Signed-off-by: David S. Miller --- drivers/net/dsa/sja1105/sja1105_mdio.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/net/dsa/sja1105/sja1105_mdio.c b/drivers/net/dsa/sja1105/sja1105_mdio.c index 19aea8fb76f6a..705d3900e43a3 100644 --- a/drivers/net/dsa/sja1105/sja1105_mdio.c +++ b/drivers/net/dsa/sja1105/sja1105_mdio.c @@ -284,8 +284,7 @@ static int sja1105_mdiobus_base_tx_register(struct sja1105_private *priv, struct mii_bus *bus; int rc = 0; - np = of_find_compatible_node(mdio_node, NULL, - "nxp,sja1110-base-tx-mdio"); + np = of_get_compatible_child(mdio_node, "nxp,sja1110-base-tx-mdio"); if (!np) return 0; @@ -339,8 +338,7 @@ static int sja1105_mdiobus_base_t1_register(struct sja1105_private *priv, struct mii_bus *bus; int rc = 0; - np = of_find_compatible_node(mdio_node, NULL, - "nxp,sja1110-base-t1-mdio"); + np = of_get_compatible_child(mdio_node, "nxp,sja1110-base-t1-mdio"); if (!np) return 0; -- 2.39.5