linux-kernel - Re: [PATCH v2] sanitize task->comm to avoid leaking escape codes

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Message-Id: <20100630092828.3903.A69D9226@jp.fujitsu.com>
Date:	Wed, 30 Jun 2010 09:31:29 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	kosaki.motohiro@...fujitsu.com,
	Kees Cook <kees.cook@...onical.com>,
	linux-kernel@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>,
	Veaceslav Falico <vfalico@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Oleg Nesterov <oleg@...hat.com>,
	Neil Horman <nhorman@...driver.com>,
	Roland McGrath <roland@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Stefani Seibold <stefani@...bold.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Eric Paris <eparis@...hat.com>,
	James Morris <jmorris@...ei.org>,
	"Andrew G. Morgan" <morgan@...nel.org>,
	Dhaval Giani <dhaval.giani@...il.com>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Steve Grubb <sgrubb@...hat.com>,
	Christoph Hellwig <hch@....de>, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v2] sanitize task->comm to avoid leaking escape codes

> > This patch sanitizes task->comm to only contain printable characters
> > when it is set.  Additionally, it redefines get_task_comm so that it is
> > more obvious when misused by callers (presently nothing was incorrectly
> > calling get_task_comm's unsafe use of strncpy).
> 
> This is a regression for tools that correctly handle unmutilated data.
> 
> > +	/* sanitize non-printable characters */
> > +	for (i = 0; buf[i] && i < (sizeof(tsk->comm) - 1); i++) {
> > +		if (!isprint(buf[i]))
> > +			tsk->comm[i] = '?';
> 
> The kernel "isprint" isn't adequate for this. comm is set by the shell
> based on argv[0] usually which means that in normal situations it is a
> UTF-8 string.

Ah, I recall one use case. In past, some IBM folks talked about they
want to map Java thread name to prctl(PR_SET_NAME). In such case, 
utf-8 name is very common.

So, I agree with you.

Thanks.



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