linux-kernel - Re: [PATCH v2 3/3] kthread: Use 'task_struct->full

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Message-ID: <202504030923.1FE7874F@keescook>
Date: Thu, 3 Apr 2025 09:24:13 -0700
From: Kees Cook <kees@...nel.org>
To: Bhupesh <bhupesh@...lia.com>
Cc: akpm@...ux-foundation.org, kernel-dev@...lia.com,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
	linux-perf-users@...r.kernel.org, linux-fsdevel@...r.kernel.org,
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	juri.lelli@...hat.com, bsegall@...gle.com, mgorman@...e.de,
	vschneid@...hat.com
Subject: Re: [PATCH v2 3/3] kthread: Use 'task_struct->full_name' to store
 kthread's full name

On Mon, Mar 31, 2025 at 05:48:20PM +0530, Bhupesh wrote:
> Commit 6986ce24fc00 ("kthread: dynamically allocate memory to store
> kthread's full name"), added 'full_name' in parallel to 'comm' for
> kthread names.
> 
> Now that we have added 'full_name' added to 'task_struct' itself,
> drop the additional 'full_name' entry from 'struct kthread' and also
> its usage.
> 
> Signed-off-by: Bhupesh <bhupesh@...lia.com>

I'd like to see this patch be the first patch in the series. This show
the existing use for "full_name". (And as such it'll probably need bits
from patch 1.)

-Kees

> ---
>  kernel/kthread.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/kthread.c b/kernel/kthread.c
> index 5dc5b0d7238e..46fe19b7ef76 100644
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -66,8 +66,6 @@ struct kthread {
>  #ifdef CONFIG_BLK_CGROUP
>  	struct cgroup_subsys_state *blkcg_css;
>  #endif
> -	/* To store the full name if task comm is truncated. */
> -	char *full_name;
>  	struct task_struct *task;
>  	struct list_head hotplug_node;
>  	struct cpumask *preferred_affinity;
> @@ -108,12 +106,12 @@ void get_kthread_comm(char *buf, size_t buf_size, struct task_struct *tsk)
>  {
>  	struct kthread *kthread = to_kthread(tsk);
>  
> -	if (!kthread || !kthread->full_name) {
> +	if (!kthread || !tsk->full_name) {
>  		strscpy(buf, tsk->comm, buf_size);
>  		return;
>  	}
>  
> -	strscpy_pad(buf, kthread->full_name, buf_size);
> +	strscpy_pad(buf, tsk->full_name, buf_size);
>  }
>  
>  bool set_kthread_struct(struct task_struct *p)
> @@ -153,7 +151,6 @@ void free_kthread_struct(struct task_struct *k)
>  	WARN_ON_ONCE(kthread->blkcg_css);
>  #endif
>  	k->worker_private = NULL;
> -	kfree(kthread->full_name);
>  	kfree(kthread);
>  }
>  
> @@ -430,7 +427,7 @@ static int kthread(void *_create)
>  		kthread_exit(-EINTR);
>  	}
>  
> -	self->full_name = create->full_name;
> +	self->task->full_name = create->full_name;
>  	self->threadfn = threadfn;
>  	self->data = data;
>  
> -- 
> 2.38.1
> 

-- 
Kees Cook