From: Ben Hutchings <ben.hutchings@codethink.co.uk>
To: dan.carpenter@oracle.com, stern@rowland.harvard.edu
Cc: stable@vger.kernel.org, stable-commits@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: Patch "USB: devio: Don't corrupt user memory" has been added to the 4.4-stable tree
Date: Tue, 17 Oct 2017 15:36:10 +0100 [thread overview]
Message-ID: <1508250970.22379.65.camel@codethink.co.uk> (raw)
In-Reply-To: <150754871438113@kroah.com>
On Mon, 2017-10-09 at 13:31 +0200, gregkh@linuxfoundation.org wrote:
[...]
> From: Dan Carpenter <dan.carpenter@oracle.com>
>
> commit fa1ed74eb1c233be6131ec92df21ab46499a15b6 upstream.
>
> The user buffer has "uurb->buffer_length" bytes. If the kernel has more
> information than that, we should truncate it instead of writing past
> the end of the user's buffer. I added a WARN_ONCE() to help the user
> debug the issue.
[...]
Users should not be able to provoke a WARN_ON at will, that's a DoS
(log spam, possible panic).
And this truncated user buffer length is also used for allocation of
the kernel buffer. Are you totally sure that this can't result in a
kernel buffer overrun (or leak)?
This fix seems worse than continuing to allow userspace to shoot itself
in the foot.
Ben.
--
Ben Hutchings
Software Developer, Codethink Ltd.
next prev parent reply other threads:[~2017-10-17 14:36 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-09 11:31 Patch "USB: devio: Don't corrupt user memory" has been added to the 4.4-stable tree gregkh
2017-10-17 14:36 ` Ben Hutchings [this message]
2017-10-17 14:48 ` Dan Carpenter
2017-10-17 14:58 ` Greg Kroah-Hartman
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