From: David Herrmann Date: Mon, 26 Aug 2013 13:16:49 +0000 (+0200) Subject: drm: fix DRM_IOCTL_MODE_GETFB handle-leak X-Git-Tag: v3.2.66~11 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=125f21f38d448ae04aae1a665147faf1263a4736;p=pandora-kernel.git drm: fix DRM_IOCTL_MODE_GETFB handle-leak commit 101b96f32956ee99bf1468afaf572b88cda9f88b upstream. DRM_IOCTL_MODE_GETFB is used to retrieve information about a given framebuffer ID. It is a read-only helper and was thus declassified for unprivileged access in: commit a14b1b42477c5ef089fcda88cbaae50d979eb8f9 Author: Mandeep Singh Baines Date: Fri Jan 20 12:11:16 2012 -0800 drm: remove master fd restriction on mode setting getters However, alongside width, height and stride information, DRM_IOCTL_MODE_GETFB also passes back a handle to the underlying buffer of the framebuffer. This handle allows users to mmap() it and read or write into it. Obviously, this should be restricted to DRM-Master. With the current setup, *any* process with access to /dev/dri/card0 (which means any process with access to hardware-accelerated rendering) can access the current screen framebuffer and modify it ad libitum. For backwards-compatibility reasons we want to keep the DRM_IOCTL_MODE_GETFB call unprivileged. Besides, it provides quite useful information regarding screen setup. So we simply test whether the caller is the current DRM-Master and if not, we return 0 as handle, which is always invalid. A following DRM_IOCTL_GEM_CLOSE on this handle will fail with EINVAL, but we accept this. Users shouldn't test for errors during GEM_CLOSE, anyway. And it is still better as a failing MODE_GETFB call. v2: add capable(CAP_SYS_ADMIN) check for compatibility with i-g-t Signed-off-by: David Herrmann Reviewed-by: Chris Wilson Signed-off-by: Dave Airlie [bwh: Backported to 3.2: - drm_framebuffer_funcs::create_handle must be non-null - Adjust context, indentation] Signed-off-by: Ben Hutchings --- Reading git-diff-tree failed