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From: Andrew Morton <akpm@linux-foundation.org>
To: Mathias Krause <minipli@googlemail.com>
Cc: linux-kernel@vger.kernel.org, Emese Revfy <re.emese@gmail.com>,
	Pax Team <pageexec@freemail.hu>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Mateusz Guzik <mguzik@redhat.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Cyrill Gorcunov <gorcunov@openvz.org>,
	Jarod Wilson <jarod@redhat.com>
Subject: Re: [PATCH] proc: prevent accessing /proc/<PID>/environ until it's ready
Date: Thu, 28 Apr 2016 14:26:22 -0700	[thread overview]
Message-ID: <20160428142622.92fad67c88152341075e4294@linux-foundation.org> (raw)
In-Reply-To: <1461870258-17970-1-git-send-email-minipli@googlemail.com>

On Thu, 28 Apr 2016 21:04:18 +0200 Mathias Krause <minipli@googlemail.com> wrote:

> If /proc/<PID>/environ gets read before the envp[] array is fully set
> up in create_{aout,elf,elf_fdpic,flat}_tables(), we might end up trying
> to read more bytes than are actually written, as env_start will already
> be set but env_end will still be zero, making the range calculation
> underflow, allowing to read beyond the end of what has been written.
> 
> Fix this as it is done for /proc/<PID>/cmdline by testing env_end for
> zero. It is, apparently, intentionally set last in create_*_tables().
> 
> This bug was found by the PaX size_overflow plugin that detected the
> arithmetic underflow of 'this_len = env_end - (env_start + src)' when
> env_end is still zero.

So what are the implications of this?  From my reading, a craftily
constructed application could occasionally read arbitrarily large
amounts of kernel memory?

  parent reply	other threads:[~2016-04-28 21:26 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-28 19:04 [PATCH] proc: prevent accessing /proc/<PID>/environ until it's ready Mathias Krause
2016-04-28 19:20 ` Mateusz Guzik
2016-04-28 19:36   ` Mathias Krause
2016-04-29 10:11   ` Alexey Dobriyan
2016-04-28 19:28 ` Cyrill Gorcunov
2016-04-28 21:26 ` Andrew Morton [this message]
2016-04-29  5:59   ` Mathias Krause
2016-04-28 21:30 ` Andrew Morton
2016-04-29  6:02   ` Mathias Krause
2016-04-29 10:25     ` Alexey Dobriyan

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