From 6be8f3bd2c78915a9f3a058a346ae93068d35c01 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Wed, 22 Aug 2018 10:54:05 +0200 Subject: [PATCH] drm/fb: Stop leaking physical address MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit For buffer sharing, use dma-buf instead. We can't set smem_start to 0 unconditionally since that's used by the fbdev mmap default implementation. And we have plenty of userspace which would like to keep that working. This might break legit userspace - if it does we need to look at a case-by-cases basis how to handle that. Worst case I expect overrides for only specific drivers, since anything remotely modern should be using dma-buf/prime now (which is about 7 years old now for DRM drivers). This issue was uncovered because Noralf's rework to implement a generic fb_probe also implements it's own fb_mmap callback. Which means smem_start didn't have to be set anymore, which blew up some blob in userspace rather badly. Acked-by: Sean Paul Cc: Gustavo Padovan Cc: Maarten Lankhorst Cc: Sean Paul Cc: David Airlie Cc: John Stultz Cc: Noralf Trønnes Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20180822085405.10787-4-daniel.vetter@ffwll.ch --- drivers/gpu/drm/drm_fb_helper.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 73cf10adebbf..8e95d0f7c71d 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -2673,6 +2673,8 @@ __drm_fb_helper_initial_config_and_unlock(struct drm_fb_helper *fb_helper, info = fb_helper->fbdev; info->var.pixclock = 0; + /* don't leak any physical addresses to userspace */ + info->flags |= FBINFO_HIDE_SMEM_START; /* Need to drop locks to avoid recursive deadlock in * register_framebuffer. This is ok because the only thing left to do is -- 2.30.2