drm/i915: Sanity check pread/pwrite

Move the access control up from the fast paths, which are no longer
universally taken first, up into the caller. This then duplicates some
sanity checking along the slow paths, but is much simpler.
Tracked as CVE-2010-2962.

Reported-by: Kees Cook <kees@ubuntu.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index cfe597865f5dd312d6528e9ce2a29eb22c48c1d4..7749e78a7300d9bebdd0f36a6ae7fbb4d97e6db0 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -477,8 +477,15 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
         */
        if (args->offset > obj->size || args->size > obj->size ||
            args->offset + args->size > obj->size) {
-               drm_gem_object_unreference_unlocked(obj);
-               return -EINVAL;
+               ret = -EINVAL;
+               goto err;
+       }
+
+       if (!access_ok(VERIFY_WRITE,
+                      (char __user *)(uintptr_t)args->data_ptr,
+                      args->size)) {
+               ret = -EFAULT;
+               goto err;
        }
 
        if (i915_gem_object_needs_bit17_swizzle(obj)) {
@@ -490,8 +497,8 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
                                                        file_priv);
        }
 
+err:
        drm_gem_object_unreference_unlocked(obj);
-
        return ret;
 }
 
@@ -580,8 +587,6 @@ i915_gem_gtt_pwrite_fast(struct drm_device *dev, struct drm_gem_object *obj,
 
        user_data = (char __user *) (uintptr_t) args->data_ptr;
        remain = args->size;
-       if (!access_ok(VERIFY_READ, user_data, remain))
-               return -EFAULT;
 
 
        mutex_lock(&dev->struct_mutex);
@@ -940,8 +945,15 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
         */
        if (args->offset > obj->size || args->size > obj->size ||
            args->offset + args->size > obj->size) {
-               drm_gem_object_unreference_unlocked(obj);
-               return -EINVAL;
+               ret = -EINVAL;
+               goto err;
+       }
+
+       if (!access_ok(VERIFY_READ,
+                      (char __user *)(uintptr_t)args->data_ptr,
+                      args->size)) {
+               ret = -EFAULT;
+               goto err;
        }
 
        /* We can only do the GTT pwrite on untiled buffers, as otherwise
@@ -975,8 +987,8 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
                DRM_INFO("pwrite failed %d\n", ret);
 #endif
 
+err:
        drm_gem_object_unreference_unlocked(obj);
-
        return ret;
 }