Re: [PATCH] backlight: check null deference of name when device is registered

On Mon, Jan 7, 2013 at 8:35 PM, Andrew Morton [off-list ref] wrote:

On Tue, 08 Jan 2013 10:25:35 +0900 Jingoo Han [off-list ref] wrote:

quoted

On Tuesday, January 08, 2013 9:02 AM, Andrew Morton wrote

quoted

On Fri, 04 Jan 2013 17:29:11 +0900
Jingoo Han [off-list ref] wrote:

quoted

NULL deference of name is checked when device is registered.
If the name is null, it will cause a kernel oops in dev_set_name().

...

--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c

@@ -292,6 +292,11 @@ struct backlight_device *backlight_device_register(const char *name,
  struct backlight_device *new_bd;
  int rc;

+ if (name = NULL) {
+         pr_err("backlight name is null\n");
+         return ERR_PTR(-EINVAL);
+ }
+
  pr_debug("backlight_device_register: name=%s\n", name);

I don't understand this.

Is there some driver which is calling these functions with name=NULL?
If so, which one(s)?

No, there is no one.

quoted

If "no" then why don't we declare that "passing name=NULL is a bug" and
leave the code as-is?

Do you mean following?

+     if (name = NULL)
+             pr_err("passing name=NULL is a bug");
+
      pr_debug("backlight_device_register: name=%s\n", name);

Nope; I'm suggesting we leave the code alone.  If someone passes in
NULL they will get a nice oops and their bug will then get fixed.

We still fail the probe in the patch Jingoo Han sent,
anyways if i catch your point correctly is this the lines you wanted?

+ /**
+  * BUG if the name of the backlight device
+  * is a NULL
+  */
+ BUG_ON(!name);