Re: [PATCH v14 11/14] tracing/wprobe: Add set_wprobe and clear_wprobe event triggers

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Calling `cancel_work_sync()` on an uninitialized `work_struct` in the error path triggers a kernel warning (WARN_ON).
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commit 5e74cd56c202daf7ad5f60c9e251b2bc86cf21d8
Author: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Subject: tracing/wprobe: Add set_wprobe and clear_wprobe event triggers

This commit adds set_wprobe and clear_wprobe event triggers to dynamically
attach and detach hardware breakpoint address monitoring based on event field
contents.

Link: https://lore.kernel.org/all/59637b96946653393a7ad3c7de094094796b39c2.1785067572.git.wangjinchao600@gmail.com/

> diff --git a/kernel/trace/trace_wprobe.c b/kernel/trace/trace_wprobe.c
> index 6a11c55e75373..29eae708ae7bc 100644
> --- a/kernel/trace/trace_wprobe.c
> +++ b/kernel/trace/trace_wprobe.c
[ ... ]
> @@ -199,14 +217,62 @@ static int __register_trace_wprobe(struct trace_wprobe *tw)
[ ... ]
>  static void free_trace_wprobe(struct trace_wprobe *tw)
>  {
>  	if (tw) {
> +		irq_work_sync(&tw->irq_work);
> +		cancel_work_sync(&tw->work);

[Severity: Medium]
Will this trigger a kernel warning in __flush_work() if the work struct has
not been initialized yet?

In alloc_trace_wprobe(), if the kstrdup() allocation for the symbol fails,
the function returns early. Since the tw pointer is managed by the
__free(free_trace_wprobe) guard, it will automatically invoke this cleanup
function:

alloc_trace_wprobe() {
    ...
    tw = kzalloc_flex(*tw, tp.args, nargs);
    ...
    if (symbol) {
        tw->symbol = kstrdup(symbol, GFP_KERNEL);
        if (!tw->symbol)
            return ERR_PTR(-ENOMEM); /* triggers free_trace_wprobe(tw) */
    }
    ...
    INIT_WORK(&tw->work, wprobe_work_func);
}

Because the early return happens before INIT_WORK() is called,
cancel_work_sync() will operate on a zeroed work_struct, which can cause a
WARN_ON(!work->func).

>  		trace_probe_cleanup(&tw->tp);
>  		kfree(tw->symbol);
>  		kfree(tw);

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Sashiko AI review · https://sashiko.dev/#/patchset/178810001186.64882.2161016469449127450.stgit@devnote2?part=11