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SubjectRe: [PATCH 1/7] phy: brcmstb-sata: add missing of_node_put


On Mon, 16 Nov 2015, Brian Norris wrote:

> On Mon, Nov 16, 2015 at 12:33:14PM +0100, Julia Lawall wrote:
> > 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 <Julia.Lawall@lip6.fr>
> >
> > ---
>
> For this patch:
>
> Acked-by: Brian Norris <computersforpeace@gmail.com>
>
> > 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);

Why not put of_node_get around dev->of_node?

julia

> 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);
> pm_runtime_disable(&phy->dev);
> device_unregister(&phy->dev);
> }
> --
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