Re: [RFC PATCH v2 10/13] mm/kwatch: add anchor thread for global watchpoints

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Medium] `kwatch_anchor_start()` overwrites `kwatch_anchor_tsk` without checking if a thread is already running, permanently leaking the previous kernel thread.
- [Low] Undefined reference to `kwatch_auto_stop` causing a linker error.
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--- Patch [10]: [RFC PATCH v2 10/13] mm/kwatch: add anchor thread for global watchpoints ---
commit a3eb869f890aaa4760c373cf20d5f98126ae7d23
Author: Jinchao Wang <wangjinchao600@gmail.com>

mm/kwatch: add anchor thread for global watchpoints

This patch adds a kernel thread that sleeps for a configured duration to
bound the watch window for global variables. When the duration expires,
the thread schedules a work item to tear down the session.

> diff --git a/mm/kwatch/anchor.c b/mm/kwatch/anchor.c
> new file mode 100644
> index 0000000000000..e87eb5e813ff2
> --- /dev/null
> +++ b/mm/kwatch/anchor.c
[ ... ]
> +static void kwatch_auto_stop_handler(struct work_struct *work)
> +{
> +	kwatch_auto_stop();
> +}

[Severity: Low]
Does this cause a linker error? kwatch_auto_stop() is called here, but it
appears to be undefined in the tree, which would result in a build failure
when CONFIG_KWATCH=y is enabled.

[ ... ]
> +int kwatch_anchor_start(u16 duration)
> +{
> +	kwatch_anchor_tsk = kthread_run(kwatch_anchor_thread_fn,
> +					(void *)(unsigned long)duration,
> +					"kwatch_anchor");
> +	if (IS_ERR(kwatch_anchor_tsk)) {

[Severity: Medium]
What happens if this function is called while an anchor thread is already
running? The global kwatch_anchor_tsk pointer is unconditionally overwritten
here without verifying if a previous thread is active or stopping it. 

Since the leaked thread loops waiting for kthread_should_stop() on a lost
task pointer, could this permanently leak the previous thread's task_struct
and stack?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260717125023.1895892-1-wangjinchao600@gmail.com?part=10