linux-kernel - [v2.6.34-stable 006/165] drm: integer overflow in drm_mode_dirtyfb

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Date:	Wed, 15 Aug 2012 15:45:50 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	<stable@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:	Xi Wang <xi.wang@...il.com>, Dave Airlie <airlied@...hat.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [v2.6.34-stable 006/165] drm: integer overflow in drm_mode_dirtyfb_ioctl()

From: Xi Wang <xi.wang@...il.com>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit a5cd335165e31db9dbab636fd29895d41da55dd2 upstream.

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@...il.com>
Signed-off-by: Xi Wang <xi.wang@...il.com>
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 drivers/gpu/drm/drm_crtc.c | 4 ++++
 include/drm/drm_mode.h     | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 1a224f8..819d0dc 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -1833,6 +1833,10 @@ 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.
  *
-- 
1.7.12.rc2

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