linux-kernel - Re: [PATCH 03/11] kthread: Pass in the thread's name during creation

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Date:   Sat, 11 Mar 2023 09:53:26 +0100
From:   Christian Brauner <brauner@...nel.org>
To:     Mike Christie <michael.christie@...cle.com>
Cc:     hch@...radead.org, stefanha@...hat.com, jasowang@...hat.com,
        mst@...hat.com, sgarzare@...hat.com,
        virtualization@...ts.linux-foundation.org, ebiederm@...ssion.com,
        torvalds@...ux-foundation.org, konrad.wilk@...cle.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/11] kthread: Pass in the thread's name during creation

On Fri, Mar 10, 2023 at 04:03:24PM -0600, Mike Christie wrote:
> This has us pass in the thread's name during creation in kernel_thread.
> 
> Signed-off-by: Mike Christie <michael.christie@...cle.com>
> ---
>  kernel/kthread.c | 35 ++++++++++++++---------------------
>  1 file changed, 14 insertions(+), 21 deletions(-)
> 
> diff --git a/kernel/kthread.c b/kernel/kthread.c
> index 63574cee925e..831a55b406d8 100644
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -38,6 +38,7 @@ struct task_struct *kthreadd_task;
>  struct kthread_create_info
>  {
>  	/* Information passed to kthread() from kthreadd. */
> +	char *full_name;
>  	int (*threadfn)(void *data);
>  	void *data;
>  	int node;
> @@ -343,10 +344,15 @@ static int kthread(void *_create)
>  	/* Release the structure when caller killed by a fatal signal. */
>  	done = xchg(&create->done, NULL);
>  	if (!done) {
> +		kfree(create->full_name);
>  		kfree(create);
>  		kthread_exit(-EINTR);
>  	}
>  
> +	if (strlen(create->full_name) >= TASK_COMM_LEN)
> +		self->full_name = create->full_name;
> +	else
> +		kfree(create->full_name);

This is monir but wwiw, this looks suspicious when reading it without
more context. It took me a while to see that kthread->full_name is
intended to store the untruncated name only if truncation actually needs
to happen. So either we should always initialize this or we should add a
comment. You can just send a tiny patch that I can fold into this one so
you don't have to resend the whole series...