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Re: [Coverity] Untrusted user data in kernel

To: linux-os@xxxxxxxxxxxx
Subject: Re: [Coverity] Untrusted user data in kernel
From: Tomas Carnecky <tom@xxxxxxxxxxxxx>
Date: Fri, 17 Dec 2004 20:18:15 +0100
Cc: Bill Davidsen <davidsen@xxxxxxx>, James Morris <jmorris@xxxxxxxxxx>, Patrick McHardy <kaber@xxxxxxxxx>, Bryan Fulton <bryan@xxxxxxxxxxxx>, netdev@xxxxxxxxxxx, netfilter-devel@xxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
In-reply-to: <Pine.LNX.4.61.0412171108340.4216@xxxxxxxxxxxxxxxxxx>
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linux-os wrote:
On Fri, 17 Dec 2004, Bill Davidsen wrote:

James Morris wrote:

On Fri, 17 Dec 2004, Patrick McHardy wrote:
That's what I meant, you need the capability to do anything bad :-)

Are you saying that processes with capability don't make mistakes? This isn't a bug related to untrusted users doing privileged operations, it's a case of using unchecked user data.

But isn't there always the possibility of "unchecked user data"?
I can, as root, do `cp /dev/zero /dev/mem` and have the most
spectacular crask you've evet seen. I can even make my file-
systems unrecoverable.

But the difference between you example (cp /dev/zero /dev/mem) and passing unchecked data to the kernel is... you _can_ check the data and do something about it if you discover that the data is not valid/within a range/whatever even if the user has full permissions. No same person would do a 'cp /dev/zero /dev/mem', but passing bad data is more likely to happen, badly written userspace configuration tools etc.


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