Daniel Vetter <dan...@ffwll.ch> writes: > On Fri, Aug 18, 2017 at 01:34:45PM -0700, Eric Anholt wrote: >> Daniel Vetter <dan...@ffwll.ch> writes: >> >> > On Fri, Aug 18, 2017 at 10:41:21AM -0700, Eric Anholt wrote: >> >> Noralf Trønnes <nor...@tronnes.org> writes: >> >> > Den 18.08.2017 09.46, skrev Daniel Vetter: >> >> >> On Thu, Aug 17, 2017 at 06:21:30PM +0200, Noralf Trønnes wrote: >> >> >>> Reject mapping an imported dma-buf since is's an invalid use-case. >> >> >>> >> >> >>> Cc: Philipp Zabel <p.za...@pengutronix.de> >> >> >>> Cc: Laurent Pinchart <laurent.pinch...@ideasonboard.com> >> >> >>> Cc: Sean Paul <seanp...@chromium.org> >> >> >>> Cc: Daniel Vetter <daniel.vet...@ffwll.ch> >> >> >>> Signed-off-by: Noralf Trønnes <nor...@tronnes.org> >> >> >> I think acks from someone using mali would be good too. amdgpu already >> >> >> has >> >> >> such checks, so I think on the desktop side we're ok. >> >> >> >> >> >> Acked-by: Daniel Vetter <daniel.vet...@ffwll.ch> >> >> >> >> >> >> But I think this one here definitely needs a few more acks. I could >> >> >> break >> >> >> uabi if we're unlucky, so let's not rush it. >> >> > >> >> > Ok, I've CC'ed the affected parties to increase the odds that they look >> >> > at this. These are the drivers using drm_gem_dumb_map_offset() >> >> > (hopefully I got the list right): >> >> >> >> If I understand the affected path right, this would break the PL111+VC4 >> >> combination: PL111 makes (dumb) buffers for scanout, and VC4 imports >> >> them and uses them for rendering. A vc4 glReadPixels of the window >> >> system buffer would map it and fail. >> > >> > It only rejects the map call on dumb buffers, and mmap on imported dma-buf >> > tends to not really work well, or at least break a few abstractions. Are >> > you sure this works currently? >> >> OK, that's right -- vc4 would be doing its "native" map call (the same >> code), not dumb map. >> >> Furthermore, I had it backwards (I had written things both ways at >> different points, iirc). We have VC4 making the buffers and PL111 >> dma-buf importing them. I don't see X11 mapping those buffers if glamor >> is enabled, so this should be OK for vc4. >> >> GBM's dumb mapping looks safe to me. X11 does some dumb maps, but I >> don't think any of those would be on imports. > > Yeah the idea is only to lock down the dumb mmap and make sure abi abuse > (which might work on a specific combo of exporters/kms drivers) is caught > for this generic interface. dumb really should only be used for > unaccelarated rendering on exactly that driver. > > So ack from you?
I'm hesitant, but that's mostly because I don't see the reason we're trying to lock it down, so it just looks like a chance of breakage from my perspective. However, given that some drivers are banning it already, let's make things consistent until we find we need to relax it globally. Acked-by: Eric Anholt <e...@anholt.net>
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