Hello Keith:
Thank you very much for your suggestion. Allow me to discuss with our
engineers.
Regards
=================================================
Bruce C. Chang(張祖明)
VIA Technologies, Inc.
Address: 1F, 531, Chung-Cheng Road, Hsin-Tien, 231 Taipei
Tel: +886-2-22185452 Ext 7323
Mobile: +886-968343824
Fax: +886-2-22186282
Skype: Bruce.C.Chang
Email: brucech...@via.com.tw
-----Original Message-----
From: Keith Whitwell [mailto:kei...@vmware.com]
Sent: Thursday, October 08, 2009 6:11 PM
To: Bruce Chang
Cc: tho...@shipmail.org; Joseph Chan; dri-devel@lists.sourceforge.net; Harald
Welte; Benjamin Chen
Subject: RE: [Patch VIA UniChrome DRM][2/5 Ver1] Add support for video command
flush and interface for V4L kernel module
On Thu, 2009-10-08 at 02:35 -0700, brucech...@via.com.tw wrote:
> Hello Thomas:
>
> > If I understand the code correctly, the user-space application
> > prepares
> > command buffers directly in AGP, and asks the
> > drm module to submit them. We can't allow this for security reasons. The
> > user-space application could for example fill the buffer with
> > commands to texture from arbitrary system memory, getting hold of other
> > user's private data.
> > The whole ring-buffer stuff and the command verifier was once
> > implemented to fix that security problem.
> Thank you very much for your comment. What if we do a security
> check in these buffer before submit? Let me check if there is any way
> to work around for this security issue.
Who would do that security check? Userspace? That doesn't work as userspace
is not trusted.
The kernel? Ok, but now it's reading commands out of a presumably
write-combined AGP buffer, which is slow. You'd have been better off passing
the commands to the kernel in regular memory, which is presumably exactly what
the existing mechanism does.
Keith
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