staging: greybus: light: fix leak of cdev->name

gb_lights_channel_config() builds the LED classdev name with kasprintf() and stores it in cdev->name for every channel during the configuration phase, which runs before the channel is registered.

That name was only released by __gb_lights_led_unregister(), i.e. only for a normal LED channel that was actually registered. It was therefore leaked in two cases:

- a channel that is configured but never registered, e.g. channel_attr_groups_set() fails, the flash configuration fails, or a later channel in the same light fails to configure and the whole light is torn down; the release path calls gb_lights_channel_unregister() (which returns early because the channel is not registered) and then gb_lights_channel_free();

- a flash, torch or indicator channel, whose unregister path (__gb_lights_flash_led_unregister()) never releases cdev->name at all, so the name leaks even on a successful teardown.

cdev->name is a configuration-phase allocation, like channel->color_name and channel->mode_name. Free it in gb_lights_channel_free() next to those, since that runs unconditionally on every teardown path, and drop the special case free from __gb_lights_led_unregister(). gb_lights_channel_unregister() is only ever called from gb_lights_channel_release(), immediately followed by gb_lights_channel_free(), so the name is still released on the registered path and is freed exactly once.

Commit 04820da21050 ("staging: greybus: light: Release memory obtained by kasprintf") fixed the leak for the registered normal-LED path only; this covers the remaining cases.

Fixes 2870b52bae4c ("greybus: lights: add lights implementation")

Signed-off-by Cong Nguyen <[email protected]>

---
 drivers/staging/greybus/light.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Quoted 32 lines · Cong Nguyen

gb_lights_channel_config() builds the LED classdev name with kasprintf() and stores it in cdev->name for every channel during the configuration phase, which runs before the channel is registered.

That name was only released by __gb_lights_led_unregister(), i.e. only for a normal LED channel that was actually registered. It was therefore leaked in two cases:

- a channel that is configured but never registered, e.g. channel_attr_groups_set() fails, the flash configuration fails, or a later channel in the same light fails to configure and the whole light is torn down; the release path calls gb_lights_channel_unregister() (which returns early because the channel is not registered) and then gb_lights_channel_free();

- a flash, torch or indicator channel, whose unregister path (__gb_lights_flash_led_unregister()) never releases cdev->name at all, so the name leaks even on a successful teardown.

cdev->name is a configuration-phase allocation, like channel->color_name and channel->mode_name. Free it in gb_lights_channel_free() next to those, since that runs unconditionally on every teardown path, and drop the special case free from __gb_lights_led_unregister(). gb_lights_channel_unregister() is only ever called from gb_lights_channel_release(), immediately followed by gb_lights_channel_free(), so the name is still released on the registered path and is freed exactly once.

Commit 04820da21050 ("staging: greybus: light: Release memory obtained by kasprintf") fixed the leak for the registered normal-LED path only; this covers the remaining cases.

Quoted 6 lines

Fixes 2870b52bae4c ("greybus: lights: add lights implementation")

Signed-off-by Cong Nguyen <[email protected]>

---
 drivers/staging/greybus/light.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Cool, but how did you find this issue? What tool did you use?

thanks,

greg k-h

Hi Greg,
I used an LLM-based agent (Claude) to flag allocations that aren't freed on error paths, then I verified this one by hand: I traced every place cdev->name (from kasprintf()) is freed and found that __gb_lights_led_unregister() misses it on the config-failure and flash channel teardown paths. No static-analysis tool was used - just the agent to surface the candidate plus manual review.

A: http://en.wikipedia.org/wiki/Top_post
Q: Were do I find info about this thing called top-posting?
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

A: No.
Q: Should I include quotations after my reply?

http://daringfireball.net/2007/07/on_top

Quoted 7 lines · Nguyễn Công

Hi Greg,
I used an LLM-based agent (Claude) to flag allocations that aren't freed on error paths, then I verified this one by hand: I traced every place cdev->name (from kasprintf()) is freed and found that __gb_lights_led_unregister() misses it on the config-failure and flash channel teardown paths. No static-analysis tool was used - just the agent to surface the candidate plus manual review.

Then please properly document this as required.

thanks,

greg k-h