amdkfd: don't open-code memdup_user()

BugLink: http://bugs.launchpad.net/bugs/1546572Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
(cherry picked from commit 8f1d57c1)
Signed-off-by: Alberto Milone <alberto.milone@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/gpu/drm/amd/amdkfd/kfd_chardev.c

@@ -559,19 +559,10 @@ static int kfd_ioctl_dbg_address_watch(struct file *filep,
 
 	/* this is the actual buffer to work with */
 
-	args_buff = kmalloc(args->buf_size_in_bytes -
-					sizeof(*args), GFP_KERNEL);
-	if (args_buff == NULL)
-		return -ENOMEM;
-
-	status = copy_from_user(args_buff, cmd_from_user,
+	args_buff = memdup_user(args_buff,
 				args->buf_size_in_bytes - sizeof(*args));
-
-	if (status != 0) {
-		pr_debug("Failed to copy address watch user data\n");
-		kfree(args_buff);
-		return -EINVAL;
-	}
+	if (IS_ERR(args_buff))
+		return PTR_ERR(args_buff);
 
 	aw_info.process = p;
 
@@ -677,22 +668,12 @@ static int kfd_ioctl_dbg_wave_control(struct file *filep,
 	if (cmd_from_user == NULL)
 		return -EINVAL;
 
-	/* this is the actual buffer to work with */
+	/* copy the entire buffer from user */
 
-	args_buff = kmalloc(args->buf_size_in_bytes - sizeof(*args),
-			GFP_KERNEL);
-
-	if (args_buff == NULL)
-		return -ENOMEM;
-
-	/* Now copy the entire buffer from user */
-	status = copy_from_user(args_buff, cmd_from_user,
+	args_buff = memdup_user(cmd_from_user,
 				args->buf_size_in_bytes - sizeof(*args));
-	if (status != 0) {
-		pr_debug("Failed to copy wave control user data\n");
-		kfree(args_buff);
-		return -EINVAL;
-	}
+	if (IS_ERR(args_buff))
+		return PTR_ERR(args_buff);
 
 	/* move ptr to the start of the "pay-load" area */
 	wac_info.process = p;