[PATCH] device property: Fix the secondary firmware node handling in set_primary_fwnode()

[PATCH] device property: Fix the secondary firmware node handling in set_primary_fwnode()

[Heikki Krogerus]

When the primary firmware node pointer is removed from a
device (set to NULL) the secondary firmware node pointer,
when it exists, is made the primary node for the device.
However, the secondary firmware node pointer of the original
primary firmware node is never cleared (set to NULL).

To avoid situation where the secondary firmware node pointer
is pointing to a non-existing object, clearing it properly
when the primary node is removed from a device in
set_primary_fwnode().

Fixes: 97badf873ab6 ("device property: Make it possible to use secondary firmware nodes")
Cc: stable@vger.kernel.org
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
---
 drivers/base/core.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index ac1046a382bc0..f6f620aa94086 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -4264,9 +4264,9 @@ static inline bool fwnode_is_primary(struct fwnode_handle *fwnode)
  */
 void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
 {
-	if (fwnode) {
-		struct fwnode_handle *fn = dev->fwnode;
+	struct fwnode_handle *fn = dev->fwnode;
 
+	if (fwnode) {
 		if (fwnode_is_primary(fn))
 			fn = fn->secondary;
 
@@ -4276,8 +4276,12 @@ void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
 		}
 		dev->fwnode = fwnode;
 	} else {
-		dev->fwnode = fwnode_is_primary(dev->fwnode) ?
-			dev->fwnode->secondary : NULL;
+		if (fwnode_is_primary(fn)) {
+			dev->fwnode = fn->secondary;
+			fn->secondary = NULL;
+		} else {
+			dev->fwnode = NULL;
+		}
 	}
 }
 EXPORT_SYMBOL_GPL(set_primary_fwnode);
-- 
2.28.0

Re: [PATCH] device property: Fix the secondary firmware node handling in set_primary_fwnode()

[Rafael J. Wysocki]

On Fri, Aug 21, 2020 at 12:53 PM Heikki Krogerus
<heikki.krogerus@linux.intel.com> wrote:
>
> When the primary firmware node pointer is removed from a
> device (set to NULL) the secondary firmware node pointer,
> when it exists, is made the primary node for the device.
> However, the secondary firmware node pointer of the original
> primary firmware node is never cleared (set to NULL).
>
> To avoid situation where the secondary firmware node pointer
> is pointing to a non-existing object, clearing it properly
> when the primary node is removed from a device in
> set_primary_fwnode().
>
> Fixes: 97badf873ab6 ("device property: Make it possible to use secondary firmware nodes")
> Cc: stable@vger.kernel.org
> Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> ---
>  drivers/base/core.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index ac1046a382bc0..f6f620aa94086 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -4264,9 +4264,9 @@ static inline bool fwnode_is_primary(struct fwnode_handle *fwnode)
>   */
>  void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
>  {
> -       if (fwnode) {
> -               struct fwnode_handle *fn = dev->fwnode;
> +       struct fwnode_handle *fn = dev->fwnode;
>
> +       if (fwnode) {
>                 if (fwnode_is_primary(fn))
>                         fn = fn->secondary;
>
> @@ -4276,8 +4276,12 @@ void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
>                 }
>                 dev->fwnode = fwnode;
>         } else {
> -               dev->fwnode = fwnode_is_primary(dev->fwnode) ?
> -                       dev->fwnode->secondary : NULL;
> +               if (fwnode_is_primary(fn)) {
> +                       dev->fwnode = fn->secondary;
> +                       fn->secondary = NULL;
> +               } else {
> +                       dev->fwnode = NULL;
> +               }
>         }
>  }
>  EXPORT_SYMBOL_GPL(set_primary_fwnode);
> --

Applied as 5.9-rc material, thanks!