[maverick, maverick/ti-omap4, natty, natty/ti-omap4 CVE 1/1] drm: integer overflow in drm_mode_dirtyfb_ioctl()

[Andy Whitcroft]

From: Xi Wang <xi.wang at gmail.com>

There is a potential integer overflow in drm_mode_dirtyfb_ioctl()
if userspace passes in a large num_clips.  The call to kmalloc would
allocate a small buffer, and the call to fb->funcs->dirty may result
in a memory corruption.

Reported-by: Haogang Chen <haogangchen at gmail.com>
Signed-off-by: Xi Wang <xi.wang at gmail.com>
Cc: stable at kernel.org
Signed-off-by: Dave Airlie <airlied at redhat.com>

(cherry picked from commit a5cd335165e31db9dbab636fd29895d41da55dd2)
CVE-2012-0044
BugLink: http://bugs.launchpad.net/bugs/917838
Signed-off-by: Andy Whitcroft <apw at canonical.com>
---
 drivers/gpu/drm/drm_crtc.c |    4 ++++
 include/drm/drm_mode.h     |    2 ++
 2 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 5f32f72..0af9a64 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -1832,6 +1832,10 @@ int drm_mode_dirtyfb_ioctl(struct drm_device *dev,
 	}
 
 	if (num_clips && clips_ptr) {
+		if (num_clips < 0 || num_clips > DRM_MODE_FB_DIRTY_MAX_CLIPS) {
+			ret = -EINVAL;
+			goto out_err1;
+		}
 		clips = kzalloc(num_clips * sizeof(*clips), GFP_KERNEL);
 		if (!clips) {
 			ret = -ENOMEM;
diff --git a/include/drm/drm_mode.h b/include/drm/drm_mode.h
index c5ba163..9cf639c 100644
--- a/include/drm/drm_mode.h
+++ b/include/drm/drm_mode.h
@@ -232,6 +232,8 @@ struct drm_mode_fb_cmd {
 #define DRM_MODE_FB_DIRTY_ANNOTATE_FILL 0x02
 #define DRM_MODE_FB_DIRTY_FLAGS         0x03
 
+#define DRM_MODE_FB_DIRTY_MAX_CLIPS     256
+
 /*
  * Mark a region of a framebuffer as dirty.
  *
-- 
1.7.5.4