linux-kernel - Re: [PATCH v4] Added PR_SET_PROCTITLE

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Date:	Tue, 3 Nov 2009 23:07:47 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Americo Wang <xiyou.wangcong@...il.com>
Cc:	kosaki.motohiro@...fujitsu.com, Timo Sirainen <tss@....fi>,
	Bryan Donlan <bdonlan@...il.com>,
	Ulrich Drepper <drepper@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-api@...r.kernel.org
Subject: Re: [PATCH v4] Added PR_SET_PROCTITLE_AREA option for prctl()

> >+		case PR_SET_PROCTITLE_AREA: {
> >+			struct mm_struct *mm = current->mm;
> >+			unsigned long addr = arg2;
> >+			unsigned long len = arg3;
> >+			unsigned long end = arg2 + arg3;
> >+
> >+			if (len > PAGE_SIZE)
> >+				return -EINVAL;
> >+
> >+			if (addr >= end)
> >+				return -EINVAL;
> >+
> >+			if (!access_ok(VERIFY_READ, addr, len))
> >+				return -EFAULT;
> >+
> >+			mutex_lock(&mm->arg_lock);
> >+			mm->arg_start = addr;
> 
> Is this safe? You're assigning a user-space pointer to kernel space...
> Don't we need copy_from_user()?

mm->arg_start, arg_end are defined so.
Please see current implementation. 


> >+			mm->arg_end = addr + len;
> 
> Since you already have 'end', no need to caculate this again. :)

Good catch :)


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