[v2.6.34-stable 132/165] drm/i915: Sanity check pread/pwrite

[Paul Gortmaker]

From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

                   -------------------
    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 ce9d419dbecc292cc3e06e8b1d6d123d3fa813a4 upstream.

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@xxxxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_gem.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e07722a..fd51c36 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -487,8 +487,15 @@ 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)) {
@@ -500,8 +507,8 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
 							file_priv);
 	}
 
+err:
 	drm_gem_object_unreference_unlocked(obj);
-
 	return ret;
 }
 
@@ -591,8 +598,6 @@ 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);
@@ -960,8 +965,15 @@ 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
@@ -994,8 +1006,8 @@ 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;
 }
 
-- 
1.7.12.rc2

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