On Mon, May 27, 2019 at 4:01 PM Thomas Hellstrom <thomas@xxxxxxxxxxxx> wrote: > > On 5/27/19 3:16 PM, Daniel Vetter wrote: > > On Mon, May 27, 2019 at 02:39:18PM +0200, Thomas Hellstrom wrote: > >> On 5/27/19 10:17 AM, Emil Velikov wrote: > >>> From: Emil Velikov <emil.velikov@xxxxxxxxxxxxx> > >>> > >>> There are cases (in mesa and applications) where one would open the > >>> primary node without properly authenticating the client. > >>> > >>> Sometimes we don't check if the authentication succeeds, but there's > >>> also cases we simply forget to do it. > >>> > >>> The former was a case for Mesa where it did not not check the return > >>> value of drmGetMagic() [1]. That was fixed recently although, there's > >>> the question of older drivers or other apps that exbibit this behaviour. > >>> > >>> While omitting the call results in issues as seen in [2] and [3]. > >>> > >>> In the libva case, libva itself doesn't authenticate the DRM client and > >>> the vaGetDisplayDRM documentation doesn't mention if the app should > >>> either. > >>> > >>> As of today, the official vainfo utility doesn't authenticate. > >>> > >>> To workaround issues like these, some users resort to running their apps > >>> under sudo. Which admittedly isn't always a good idea. > >>> > >>> Since any DRIVER_RENDER driver has sufficient isolation between clients, > >>> we can use that, for unauthenticated [primary node] ioctls that require > >>> DRM_AUTH. But only if the respective ioctl is tagged as DRM_RENDER_ALLOW. > >>> > >>> v2: > >>> - Rework/simplify if check (Daniel V) > >>> - Add examples to commit messages, elaborate. (Daniel V) > >>> > >>> v3: > >>> - Use single unlikely (Daniel V) > >>> > >>> v4: > >>> - Patch was reverted because it broke AMDGPU, apply again. The AMDGPU > >>> issue is fixed with earlier patch. > >>> > >>> [1] https://gitlab.freedesktop.org/mesa/mesa/blob/2bc1f5c2e70fe3b4d41f060af9859bc2a94c5b62/src/egl/drivers/dri2/platform_wayland.c#L1136 > >>> [2] https://lists.freedesktop.org/archives/libva/2016-July/004185.html > >>> [3] https://gitlab.freedesktop.org/mesa/kmscube/issues/1 > >>> Testcase: igt/core_unauth_vs_render > >>> Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx > >>> Signed-off-by: Emil Velikov <emil.velikov@xxxxxxxxxxxxx> > >>> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > >>> Link: https://patchwork.freedesktop.org/patch/msgid/20190114085408.15933-2-emil.l.velikov@xxxxxxxxx > >>> --- > >>> drivers/gpu/drm/drm_ioctl.c | 20 ++++++++++++++++---- > >>> 1 file changed, 16 insertions(+), 4 deletions(-) > >>> > >>> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c > >>> index 9841c0076f02..b64b022a2b29 100644 > >>> --- a/drivers/gpu/drm/drm_ioctl.c > >>> +++ b/drivers/gpu/drm/drm_ioctl.c > >>> @@ -511,6 +511,13 @@ int drm_version(struct drm_device *dev, void *data, > >>> return err; > >>> } > >>> +static inline bool > >>> +drm_render_driver_and_ioctl(const struct drm_device *dev, u32 flags) > >>> +{ > >>> + return drm_core_check_feature(dev, DRIVER_RENDER) && > >>> + (flags & DRM_RENDER_ALLOW); > >>> +} > >>> + > >>> /** > >>> * drm_ioctl_permit - Check ioctl permissions against caller > >>> * > >>> @@ -525,14 +532,19 @@ int drm_version(struct drm_device *dev, void *data, > >>> */ > >>> int drm_ioctl_permit(u32 flags, struct drm_file *file_priv) > >>> { > >>> + const struct drm_device *dev = file_priv->minor->dev; > >>> + > >>> /* ROOT_ONLY is only for CAP_SYS_ADMIN */ > >>> if (unlikely((flags & DRM_ROOT_ONLY) && !capable(CAP_SYS_ADMIN))) > >>> return -EACCES; > >>> - /* AUTH is only for authenticated or render client */ > >>> - if (unlikely((flags & DRM_AUTH) && !drm_is_render_client(file_priv) && > >>> - !file_priv->authenticated)) > >>> - return -EACCES; > >>> + /* AUTH is only for master ... */ > >>> + if (unlikely((flags & DRM_AUTH) && drm_is_primary_client(file_priv))) { > >>> + /* authenticated ones, or render capable on DRM_RENDER_ALLOW. */ > >>> + if (!file_priv->authenticated && > >>> + !drm_render_driver_and_ioctl(dev, flags)) > >>> + return -EACCES; > >>> + } > >> This breaks vmwgfx primary client authentication in the surface_reference > >> ioctl, which takes different paths in case of render clients and primary > >> clients, but adding an auth check in the primary path in the vmwgfx code > >> should fix this. > > Hm yeah we need to adjust that ... otoh kinda not sure why this is gated > > on authentication status, and not on "am I master or not" status. At least > > from a very cursory read ... > > -Daniel > > The code snippet in question is: > > > if (drm_is_primary_client(file_priv) && > user_srf->master != file_priv->master) { > DRM_ERROR("Trying to reference surface outside of" > " master domain.\n"); > ret = -EACCES; > goto out_bad_resource; > } > > > In gem term's this means a client can't open a surface that hasn't been > flinked by a client in the same master realm: You can't read from > resources belonging to another X server's clients.... Uh, I read something completely different in there. I guess I didn't really follow what's going on there :-) -Daniel > > /Thomas > > > > > > >> /Thomas > >> > >> > >>> /* MASTER is only for master or control clients */ > >>> if (unlikely((flags & DRM_MASTER) && > >> > >> _______________________________________________ > >> dri-devel mailing list > >> dri-devel@xxxxxxxxxxxxxxxxxxxxx > >> https://lists.freedesktop.org/mailman/listinfo/dri-devel > > -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
