drm/i915: fix integer overflow in i915_gem_do_execbuffer()

On 32-bit systems, a large args->num_cliprects from userspace via ioctl
may overflow the allocation size, leading to out-of-bounds access.

This vulnerability was introduced in commit 432e58ed ("drm/i915: Avoid
allocation for execbuffer object list").

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 7c50e58..de43194 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1133,6 +1133,11 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
                        return -EINVAL;
                }
 
+               if (args->num_cliprects > UINT_MAX / sizeof(*cliprects)) {
+                       DRM_DEBUG("execbuf with %u cliprects\n",
+                                 args->num_cliprects);
+                       return -EINVAL;
+               }
                cliprects = kmalloc(args->num_cliprects * sizeof(*cliprects),
                                    GFP_KERNEL);
                if (cliprects == NULL) {