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Subject[006/104] drm: integer overflow in drm_mode_dirtyfb_ioctl()
3.1-stable review patch.  If anyone has any objections, please let me know.

------------------

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

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@gmail.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/gpu/drm/drm_crtc.c | 4 ++++
include/drm/drm_mode.h | 2 ++
2 files changed, 6 insertions(+)

--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -1868,6 +1868,10 @@ int drm_mode_dirtyfb_ioctl(struct drm_de
}

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;
--- a/include/drm/drm_mode.h
+++ b/include/drm/drm_mode.h
@@ -233,6 +233,8 @@ 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.
*



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