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From: Bryan Donlan <bdonlan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Cc: KOSAKI Motohiro
	<kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org>,
	Americo Wang
	<xiyou.wangcong-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Timo Sirainen <tss-X3B1VOXEql0@public.gmane.org>,
	Ulrich Drepper <drepper-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v5] Added PR_SET_PROCTITLE_AREA option for prctl()
Date: Mon, 9 Nov 2009 19:00:17 -0500	[thread overview]
Message-ID: <3e8340490911091600v3a0e9b67r279349ac852d604a@mail.gmail.com> (raw)
In-Reply-To: <20091109144717.0cd17421.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>

On Mon, Nov 9, 2009 at 5:47 PM, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3Sm6D+HspMUB@public.gmane.orgg> wrote:

> What happens if userspace unmaps the memory after telling the kernel to
> use it?
>
> Will processes which try to read the command line get an error reading
> /proc?  If so, do all the commandline-reading programs in the world
> handle this in an appropriate fashion?

This case can already occur in the current code; the userspace process
would have to munmap() the top of its stack, but it certainly can do
so if it tries. In any case, access_process_vm() then returns 0
because of the fault, and thus /proc/pid/cmdline is seen to have zero
length. Since a zero-length /proc/pid/cmdline occurs with kernel
threads as well, we know this isn't a problem.

  parent reply	other threads:[~2009-11-10  0:00 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20091101211321.F3FC.A69D9226@jp.fujitsu.com>
     [not found] ` <20091101211321.F3FC.A69D9226-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
2009-11-03  9:47   ` [PATCH v4] Added PR_SET_PROCTITLE_AREA option for prctl() Américo Wang
     [not found]     ` <20091103094703.GB11134-lyUE10xJyvyny3qCrzbmXA@public.gmane.org>
2009-11-03 14:07       ` KOSAKI Motohiro
     [not found]         ` <20091103230548.0B45.A69D9226-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
2009-11-03 15:26           ` [PATCH v5] " KOSAKI Motohiro
     [not found]             ` <20091104002544.0B4A.A69D9226-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
2009-11-03 16:12               ` Américo Wang
2009-11-09 22:47             ` Andrew Morton
     [not found]               ` <20091109144717.0cd17421.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2009-11-10  0:00                 ` Bryan Donlan [this message]
2009-11-10 11:06                   ` KOSAKI Motohiro

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