linux-kernel - Re: [PATCH 1/5] kernel: replace sizeof(task->comm) with TASK_COMM

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Date:   Sun, 3 Oct 2021 03:31:39 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     akpm@...ux-foundation.org, pmladek@...e.com, peterz@...radead.org,
        valentin.schneider@....com, keescook@...omium.org,
        mathieu.desnoyers@...icios.com, qiang.zhang@...driver.com,
        robdclark@...omium.org, christian@...uner.io,
        dietmar.eggemann@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] kernel: replace sizeof(task->comm) with TASK_COMM_LEN

On Wed, Sep 29, 2021 at 11:50:32AM +0000, Yafang Shao wrote:

> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -2265,7 +2265,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
>  		unsigned long, arg4, unsigned long, arg5)
>  {
>  	struct task_struct *me = current;
> -	unsigned char comm[sizeof(me->comm)];
> +	unsigned char comm[TASK_COMM_LEN];
>  	long error;
>  
>  	error = security_task_prctl(option, arg2, arg3, arg4, arg5);

Slightly below you have this:
        case PR_SET_NAME:
                comm[sizeof(me->comm) - 1] = 0;
                if (strncpy_from_user(comm, (char __user *)arg2,
                                      sizeof(me->comm) - 1) < 0)
                        return -EFAULT;
                set_task_comm(me, comm);
                proc_comm_connector(me);
                break;

How had that been tested?