From: Keith Owens <kaos@ocs.com.au>
To: linux-kernel@vger.kernel.org
Subject: Re: Local DoS on single_open?
Date: Thu, 11 Sep 2003 17:26:54 +1000 [thread overview]
Message-ID: <5311.1063265214@kao2.melbourne.sgi.com> (raw)
In-Reply-To: Your message of "Thu, 11 Sep 2003 05:55:07 +0100." <20030911045507.GQ454@parcelfarce.linux.theplanet.co.uk>
On Thu, 11 Sep 2003 05:55:07 +0100,
viro@parcelfarce.linux.theplanet.co.uk wrote:
>On Thu, Sep 11, 2003 at 02:42:13PM +1000, Keith Owens wrote:
>> single_open() requires the kernel to kmalloc a buffer which lives until
>> the userspace caller closes the file. What prevents a malicious user
>> opening the same /proc entry multiple times, allocating lots of kmalloc
>> space and causing a local DoS?
>
>Size of that buffer is limited. IOW, it's not different from opening
>e.g. a shitload of pipes or sockets.
In some cases, the buffer size is set to hold _all_ of the output for
that particular /proc file and will be much larger than the data
reserved for files and sockets. It is a difference in scale.
fs/proc/proc_misc.c stat_open
fs/proc/proc_misc.c interrupts_open
kernel/dma.c proc_dma_open
All those functions will kmalloc a reasonably sized buffer then let the
user control the lifetime of that buffer. Looks like a recipe for a
local DoS to me.
next prev parent reply other threads:[~2003-09-11 7:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-11 4:42 Local DoS on single_open? Keith Owens
2003-09-11 4:51 ` Nick Piggin
2003-09-11 7:04 ` Keith Owens
2003-09-11 7:29 ` viro
2003-09-11 4:55 ` viro
2003-09-11 7:26 ` Keith Owens [this message]
2003-09-11 7:32 ` viro
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