linux-kernel - Re: [PATCH v2] Make PTRACE_SEIZE set ptrace options specified in 'data' parameter

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Message-ID: <20110908004438.GC3987@mtj.dyndns.org>
Date:	Thu, 8 Sep 2011 09:44:38 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Denys Vlasenko <vda.linux@...glemail.com>
Cc:	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	dvlasenk@...hat.com
Subject: Re: [PATCH v2] Make PTRACE_SEIZE set ptrace options specified in
 'data' parameter

Hello,

On Wed, Sep 07, 2011 at 11:40:31PM +0200, Denys Vlasenko wrote:
> +	if (seize) {
> +		if (addr != 0)
> +			goto out;
> +		if ((flags & ~(long)PTRACE_O_MASK) != PTRACE_SEIZE_DEVEL)

Please use (unsigned long).  Also, wouldn't it be better to do the
following instead?

	if (!(flags & PTRACE_SEIZE_DEVEL))
		goto out;
	flags &= ~PTRACE_SEIZE_DEVEL;

	if ((flags & ~(unsigned long(PTRACE_O_MASK))))
		goto out;

Then, we can later just delete the first three lines when removing
SEIZE_DEVEL.

> @@ -263,11 +272,9 @@ static int ptrace_attach(struct task_struct *task, long request,
>  	if (task->ptrace)
>  		goto unlock_tasklist;
>  
> -	task->ptrace = PT_PTRACED;
> -	if (seize)
> -		task->ptrace |= PT_SEIZED;
>  	if (task_ns_capable(task, CAP_SYS_PTRACE))
> -		task->ptrace |= PT_PTRACE_CAP;
> +		flags |= PT_PTRACE_CAP;
> +	task->ptrace = flags;

Can you please put this in a separate patch?  Hmm... also I think we
probably want to set ->ptrace while holding siglock too.  There are
places which assume ->ptrace is protected by siglock.  We can move
siglock locking above so that both ->ptrace setting and linking are
protected by siglock and use send_signal() instead of send_sig_info()
for the implied SIGSTOP.  Note that __ptrace_unlink() would need
similar update too.

Thank you.

-- 
tejun
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