On Mon, Nov 16, 2015 at 12:33:14PM +0100, Julia Lawall wrote:

quoted

for_each_available_child_of_node performs an of_node_get on each iteration,
so a return from the middle of the loop requires an of_node_put.

A simplified version of the semantic patch that finds this problem is as
follows (http://coccinelle.lip6.fr):

// <smpl>
@@
expression root,e;
local idexpression child;
@@

 for_each_available_child_of_node(root, child) {
   ... when != of_node_put(child)
       when != e = child
(
   return child;
|
*  return ...;
)
   ...
 }
// </smpl>

Signed-off-by: Julia Lawall <redacted>

---

For this patch:

Acked-by: Brian Norris <computersforpeace@gmail.com>

quoted

 drivers/phy/phy-brcmstb-sata.c |   17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

[snip patch, which fixes of_node_put() handling for
for_each_available_child_of_node() loop, which creates PHY devices with
devm_phy_create()]

This reminds me of a potential problem I'm looking at in other
subsystems: from code reading (I haven't seen any issues in practice,
probably because I don't use OF_DYNAMIC) it looks like device-creating
infrastructure like the PHY subsystem should be acquiring a reference to
the device_node when they stash it away. But drivers/phy/phy-core.c does
not do this, AFAICT.

See phy_create(), which does

	phy->dev.of_node = node ?: dev->of_node;

and later might reuse this of_node pointer, even though it never called
of_node_get() on this node.

Potential patch to fix this (not tested).

Signed-off-by: Brian Norris <computersforpeace@gmail.com>

diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
index fc48fac003a6..8df29caeeef9 100644
--- a/drivers/phy/phy-core.c
+++ b/drivers/phy/phy-core.c

@@ -697,6 +697,7 @@ struct phy *phy_create(struct device *dev, struct device_node *node,
 	phy->dev.class = phy_class;
 	phy->dev.parent = dev;
 	phy->dev.of_node = node ?: dev->of_node;
+	of_node_get(phy->dev.of_node);
 	phy->id = id;
 	phy->ops = ops;
 

@@ -726,6 +727,7 @@ struct phy *phy_create(struct device *dev, struct device_node *node,
 	return phy;
 
 put_dev:
+	of_node_put(phy->dev.of_node);
 	put_device(&phy->dev);  /* calls phy_release() which frees resources */
 	return ERR_PTR(ret);
 

@@ -775,6 +777,7 @@ EXPORT_SYMBOL_GPL(devm_phy_create);
  */
 void phy_destroy(struct phy *phy)
 {
+	of_node_put(phy->dev.of_node);