[PATCH 19/21] drm/i915: Rephrase pwrite bounds checking to avoid any potential overflow

[Chris Wilson]

commit 7dcd2499deab8f10011713c40bc2f309c9b65077 upstream.

... and do the same for pread.

Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxx

[Backported to Debian's 2.6.32 by dann frazier <dannf@xxxxxxxxxx>]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Signed-off-by: Stefan Bader <stefan.bader@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_gem.c |   16 ++++------------
 1 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 366abe3..a34fd44 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -482,12 +482,8 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
 		return -EBADF;
 	obj_priv = obj->driver_private;

-	/* Bounds check source.
-	 *
-	 * XXX: This could use review for overflow issues...
-	 */
-	if (args->offset > obj->size || args->size > obj->size ||
-	    args->offset + args->size > obj->size) {
+	/* Bounds check source.  */
+	if (args->offset > obj->size || args->size > obj->size - args->offset) {
 		ret = -EINVAL;
 		goto err;
 	}
@@ -960,12 +956,8 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
 		return -EBADF;
 	obj_priv = obj->driver_private;

-	/* Bounds check destination.
-	 *
-	 * XXX: This could use review for overflow issues...
-	 */
-	if (args->offset > obj->size || args->size > obj->size ||
-	    args->offset + args->size > obj->size) {
+	/* Bounds check destination. */
+	if (args->offset > obj->size || args->size > obj->size - args->offset) {
 		ret = -EINVAL;
 		goto err;
 	}
--
1.7.0.4

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