Re: [PATCH] HID: wacom: Cancel init_work when probe fails after scheduling it

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Uncancelled background workers and timers in the wacom_parse_and_register() error path lead to UAF when called outside of probe().
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commit 611f293eb48407c71bbdfd98b12f13ec53358ab0
Author: Aamir Ahmed <elb12345@hotmail.co.uk>

HID: wacom: Cancel init_work when probe fails after scheduling it

This commit cancels init_work on the shared error path in
wacom_parse_and_register() to prevent a use-after-free when probe fails
and devres cleans up driver resources.

Closes: https://lore.kernel.org/linux-input/20260905102908.ADE1F1F00A3D@smtp.kernel.org/

> diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c
> index 0eafa483b7f75..ba8adefd93266 100644
> --- a/drivers/hid/wacom_sys.c
> +++ b/drivers/hid/wacom_sys.c
[ ... ]
> @@ -2501,6 +2501,7 @@ static int wacom_parse_and_register(struct wacom *wacom, bool wireless)
>  
>  fail_hw_stop:
>  	hid_hw_stop(hdev);
> +	cancel_delayed_work_sync(&wacom->init_work);
>  fail:
>  	wacom_release_resources(wacom);
>  	return error;

[Severity: High]
This is a pre-existing issue, but can this error path still result in a
use-after-free if it is reached outside of probe()?

The commit message notes that reports cannot reach the driver during probe
because driver_input_lock is held, preventing other work items from being
scheduled.

However, looking at wacom_wireless_work() and wacom_mode_change_work(),
they also call wacom_parse_and_register(). In these workqueue contexts,
driver_input_lock is not held.

Once hid_hw_start() is called earlier in this function, could incoming
reports immediately schedule asynchronous tasks like remote_work,
battery_work, and aes_battery_work?

If a subsequent step like hid_hw_open() fails, execution jumps to
fail_hw_stop. While init_work is cancelled here, the other background
tasks are not.

Will wacom_release_resources() then free the devres group containing
wacom->remote and other structures, leaving those uncancelled tasks to
execute and access freed memory?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/PAXP251MB001050EFD88752318EBA75F5C8B42@PAXP251MB0010.EURP251.PROD.OUTLOOK.COM?part=1