On 08/22/2018 10:54 AM, Daniel Vetter wrote:
DRM drivers really, really, really don't want random userspace to share buffer behind it's back, bypassing the dma-buf buffer sharing machanism. For that reason we've ruthlessly rejected any IOCTL exposing the physical address of any graphics buffer.
Unfortunately fbdev comes with that built-in. We could just set smem_start to 0, but that means we'd have to hand-roll our own fb_mmap implementation. For good reasons many drivers do that, but smem_start/length is still super convenient.
Hence instead just stop the leak in the ioctl, to keep fb mmap working as-is. A second patch will set this flag for all drm drivers.
Cc: Bartlomiej Zolnierkiewicz b.zolnierkie@samsung.com Cc: Kees Cook keescook@chromium.org Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: linux-fbdev@vger.kernel.org Signed-off-by: Daniel Vetter daniel.vetter@intel.com
Acked-by: Bartlomiej Zolnierkiewicz b.zolnierkie@samsung.com
Best regards, -- Bartlomiej Zolnierkiewicz Samsung R&D Institute Poland Samsung Electronics