From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Sun, 26 Sep 2010 19:50:05 +0000 (+0100)
Subject: drm/i915: Sanity check pread/pwrite
X-Git-Tag: v2.6.36-rc7~17^2~1
X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=ce9d419dbecc292cc3e06e8b1d6d123d3fa813a4

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 cfe5978..7749e78 100644
--- 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;
 }