On Wed, Oct 10, 2018 at 07:35:06PM +0200, Max Reitz wrote: > On 10.10.18 12:10, Gerd Hoffmann wrote: > > On Mon, Oct 08, 2018 at 08:50:13PM +0200, Max Reitz wrote: > >> There are some 2D resource formats that can be used through virtio-gpu, > > > > Ahem, not really. XRGB is the only one which works in practice, and > > virtio-gpu kms driver will stop advertising anything else soon (patches > > should land upstream with the next merge window). > > OK, if virtio-gpu didn't support anything else, that'd be a fix, too. > But it sounds like you're talking about the Linux driver, I'm not. > > This is not about Linux applications being able to abuse the Linux > driver to crash the VM, this is about malicious drivers (not necessarily > Linux drivers). > > >> Add these formats in the switch converting pixman to SDL format > >> constants so a guest cannot crash the VM by triggering the > >> g_assert_not_reached() with an unsupported format. > > > > Do you have a reproducer for that? > > I have attached two RISC-V kernels, one (kernel-rgbx) setting > VIRTIO_GPU_FORMAT_R8G8B8X8_UNORM, the other (kernel-bgra) setting > VIRTIO_GPU_FORMAT_B8G8R8A8_UNORM. Both crash qemu: > > $ $QEMU/build/riscv64-softmmu/qemu-system-riscv64 -kernel kernel-rgbx \ > -serial stdio -M virt -device virtio-gpu-device > [platform-virt] Virt platform detected > [virtio-gpu] Found device @0x10008000 > [virtio-gpu] Scanout 0: 0x0:1024x768 > ** > ERROR:$QEMU/ui/sdl2-2d.c:114:sdl2_2d_switch: code should not be reached > [1] 7151 abort (core dumped)
Ok, I see. If sdl2 can support those formats it makes sense to support them, but they must be added to both sdl2_2d_check_format() and sdl2_2d_switch() then. > > There is sdl2_2d_check_format() which reports the supported formats. > > If we hit sdl2_2d_switch() with a format not whitelisted by > > sdl2_2d_check_format() we have a bug somewhere in qemu ... > > I suppose the other solution would be for virtio_gpu_set_scanout() to > check whether the resource's format can actually be used for that > display. Yes, that must be added (independent from the sdl2 patch). > Or in virtio_gpu_resource_create_2d(), I don't know whether > it's possible to use resources in other formats at all. Not directly, they must be converted (using pixman) then. cheers, Gerd