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https://bugs.freedesktop.org/show_bug.cgi?id=6242
------- Additional Comments From [EMAIL PROTECTED] 2006-04-01 06:39 -------
(In reply to comment #6)
> (In reply to comment #5)
> > Created an attachment (id=5123)
--> (https://bugs.freedesktop.org/attachment.cgi?id=5123&action=view) [edit]
[edit]
> > mach64-drm: DMA buffers for vertices - try 2
> >
> > enable test of register values in the vertex buffer.
>
> It's good to see this driver getting some attention again, I'm sorry I don't
> have time to help out with the code right now.
>
> I wanted to point out that if you go this route (using client DMA buffers for
> vertices), you'll need to unmap the buffers from userspace before verifying
> and
> submitting them to make this secure. If you look at the CVS history, you'll
> see
> that we actually used to use DMA buffers, but changed to the current method
> when
> beginning the work to make the driver secure. We decided that copying the
> data
> from client memory into a pool of unmapped DMA buffers in the kernel would be
> faster than unmapping and re-mapping the buffers for each submit. Copying the
> userspace data into DMA buffers allocated from the mapped pool was a stopgap
> until we had a way to allocate unmapped buffers in the kernel for this
> purpose.
>
Grrh, I knew I was missing something basic when I tried to touch this stuff ...
also a bit stupid of me to lurk and search mesa-dev for mach64 DMA instead of
dri-devel.
I'll probably do my "homework" over the weekend. Just a question to make sure I
am not completely mixed up: As it stands now, is drm_blit secure ? I mean a
malicious client can still change the contents of the DMA buffer after
submission to the drm in the case of a blit also, esp. the first
MACH64_HOSTDATA_BLIT_OFFSET bytes.
> It's been a while since I looked at the code in detail, but the problem at the
> time was a limitation of the DRM buffer management infrastructure. As I
> recall,
> there wasn't an easy way to create two sets of DMA buffers, one mapped to
> userspace, and one which wasn't mapped. You may want to look into the mailing
> list archives for more discussion on this. I think that this was the last
> remaining issue in securing the driver.
>
> -Leif
Thanks for your comments and your work on open source drivers,
george.
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