On 2/15/20 9:11 PM, qiwuchen55@xxxxxxxxx wrote:
> From: chenqiwu <chenqiwu@xxxxxxxxxx>
>
> safe_name() tries to find a non-existing name of kernfs_node
> by sysfs_get_dirent() no more than 16 times.
>
> There are three possible results when while loop breaks:
> 1. i = 0, name = orig_name, name is safe to use.
> 2. i > 0 && i < 16, name != orig_name, name is safe to use.
> 3. i == 16, name != orig_name, name is unsafe to use.
>
> However, the original code consider 2nd result as unsafe with
> a unnecessary warning message by pr_warn(). This patch can fix
> the problem.
No, the warning for case 2 is appropriate.
The result of the rename is that the contents of /proc/device-tree
are not equivalent to the devicetree. It is valuable to know this
has occurred.
The only way I know of for the rename to occur is if a node contains
both a property and a node with the same name. This should not occur
if the name conventions for properties and nodes are followed.
If anyone is aware of a scenario where variable i can be greater
than 1, please let me know.
-Frank
>
> Signed-off-by: chenqiwu <chenqiwu@xxxxxxxxxx>
> ---
> drivers/of/kobj.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/of/kobj.c b/drivers/of/kobj.c
> index c72eef9..b32cf55 100644
> --- a/drivers/of/kobj.c
> +++ b/drivers/of/kobj.c
> @@ -52,11 +52,14 @@ static const char *safe_name(struct kobject *kobj, const char *orig_name)
> }
>
> if (name == orig_name) {
> - name = kstrdup(orig_name, GFP_KERNEL);
> - } else {
> + name = kstrdup_const(orig_name, GFP_KERNEL);
> + return name;
> + }
> +
> + if (i == 16)
> pr_warn("Duplicate name in %s, renamed to \"%s\"\n",
> kobject_name(kobj), name);
> - }
> +
> return name;
> }
>
>
