Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756020Ab3I2T3Z (ORCPT ); Sun, 29 Sep 2013 15:29:25 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59700 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755924Ab3I2T3N (ORCPT ); Sun, 29 Sep 2013 15:29:13 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Herrmann , Chris Wilson , Dave Airlie Subject: [ 28/71] drm: fix DRM_IOCTL_MODE_GETFB handle-leak Date: Sun, 29 Sep 2013 12:27:40 -0700 Message-Id: <20130929192645.437642542@linuxfoundation.org> X-Mailer: git-send-email 1.8.4.6.g82e253f.dirty In-Reply-To: <20130929192643.539596256@linuxfoundation.org> References: <20130929192643.539596256@linuxfoundation.org> User-Agent: quilt/0.60-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3053 Lines: 81 3.11-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Herrmann 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 Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_crtc.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) --- a/drivers/gpu/drm/drm_crtc.c +++ b/drivers/gpu/drm/drm_crtc.c @@ -2604,10 +2604,22 @@ int drm_mode_getfb(struct drm_device *de r->depth = fb->depth; r->bpp = fb->bits_per_pixel; r->pitch = fb->pitches[0]; - if (fb->funcs->create_handle) - ret = fb->funcs->create_handle(fb, file_priv, &r->handle); - else + if (fb->funcs->create_handle) { + if (file_priv->is_master || capable(CAP_SYS_ADMIN)) { + ret = fb->funcs->create_handle(fb, file_priv, + &r->handle); + } else { + /* GET_FB() is an unprivileged ioctl so we must not + * return a buffer-handle to non-master processes! For + * backwards-compatibility reasons, we cannot make + * GET_FB() privileged, so just return an invalid handle + * for non-masters. */ + r->handle = 0; + ret = 0; + } + } else { ret = -ENODEV; + } drm_framebuffer_unreference(fb); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/