[PATCH 3/7] drm/syncobj: Avoid one temporary allocation in drm_syncobj_array_find

[Tvrtko Ursulin <tursulin@xxxxxxxxxx>]

From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>

Drm_syncobj_array_find() helper is used from many userspace ioctl entry
points with the task of looking up userspace handles to internal objects.

We can easily avoid one temporary allocation by making it read the handles
as it is looking them up.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>
---
 drivers/gpu/drm/drm_syncobj.c | 44 +++++++++++++++++------------------
 1 file changed, 21 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index fd5ba6c89666..cdda2df06bec 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -1213,48 +1213,46 @@ signed long drm_timeout_abs_to_jiffies(int64_t timeout_nsec)
 EXPORT_SYMBOL(drm_timeout_abs_to_jiffies);
 
 static int drm_syncobj_array_find(struct drm_file *file_private,
-				  void __user *user_handles,
-				  uint32_t count_handles,
+				  u32 __user *handles,
+				  uint32_t count,
 				  struct drm_syncobj ***syncobjs_out)
 {
-	uint32_t i, *handles;
 	struct drm_syncobj **syncobjs;
+	uint32_t i;
 	int ret;
 
-	handles = kmalloc_array(count_handles, sizeof(*handles), GFP_KERNEL);
-	if (handles == NULL)
+	if (!access_ok(handles, count * sizeof(*handles)))
+		return -EFAULT;
+
+	syncobjs = kmalloc_array(count, sizeof(*syncobjs), GFP_KERNEL);
+	if (!syncobjs)
 		return -ENOMEM;
 
-	if (copy_from_user(handles, user_handles,
-			   sizeof(uint32_t) * count_handles)) {
-		ret = -EFAULT;
-		goto err_free_handles;
-	}
+	for (i = 0; i < count; i++) {
+		u64 handle;
 
-	syncobjs = kmalloc_array(count_handles, sizeof(*syncobjs), GFP_KERNEL);
-	if (syncobjs == NULL) {
-		ret = -ENOMEM;
-		goto err_free_handles;
-	}
-
-	for (i = 0; i < count_handles; i++) {
-		syncobjs[i] = drm_syncobj_find(file_private, handles[i]);
+		if (__get_user(handle, handles++)) {
+			ret = -EFAULT;
+			syncobjs[i] = NULL;
+			goto err_put_syncobjs;
+		}
+		syncobjs[i] = drm_syncobj_find(file_private, handle);
 		if (!syncobjs[i]) {
 			ret = -ENOENT;
 			goto err_put_syncobjs;
 		}
 	}
 
-	kfree(handles);
 	*syncobjs_out = syncobjs;
 	return 0;
 
 err_put_syncobjs:
-	while (i-- > 0)
-		drm_syncobj_put(syncobjs[i]);
+	while (i > 0) {
+		if (syncobjs[i])
+			drm_syncobj_put(syncobjs[i]);
+		i--;
+	}
 	kfree(syncobjs);
-err_free_handles:
-	kfree(handles);
 
 	return ret;
 }
-- 
2.47.1