linux-kernel - Re: [PATCH 1/1] coredump: use task comm instead of (unknown)

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Message-Id: <201105080037.GFD90166.HFMQVLOSFOtFJO@I-love.SAKURA.ne.jp>
Date:	Sun, 8 May 2011 00:37:34 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	akpm@...ux-foundation.org
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	john.stultz@...aro.org
Subject: Re: [PATCH 1/1] coredump: use task comm instead of (unknown)

Andrew Morton wrote:
> PR_SET_NAME uses set_task_comm() which has appropriate locking to
> protect against get_task_comm().  
> 
> If kernel code directly accesses task->comm without taking task_lock()
> then yes, it's racy.

I see. Well,

  grep -r -- '->comm[,;)]' .

in 2.6.39-rc6 shows so many users directly reading/updating, including

	case 'e':
		err = cn_printf(cn, "%s", current->comm);
		break;

in format_corename().

> Hopefully John Stultz will soon be presenting us with a %p modifier for
> displaying task_struct.comm.

That will be nice. But caller might by error call printk() with that modifier
between task_lock() and task_unlock().
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