From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S965949AbdIYT4H (ORCPT <rfc822;w@1wt.eu>);
        Mon, 25 Sep 2017 15:56:07 -0400
Received: from Galois.linutronix.de ([146.0.238.70]:46181 "EHLO
        Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S932107AbdIYT4G (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 25 Sep 2017 15:56:06 -0400
Date: Mon, 25 Sep 2017 21:56:00 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Ingo Molnar <mingo@kernel.org>
cc: linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Eric Biggers <ebiggers3@gmail.com>,
        Andy Lutomirski <luto@amacapital.net>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>, "H . Peter Anvin" <hpa@zytor.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
        Rik van Riel <riel@redhat.com>, Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: Re: [PATCH 08/33] x86/fpu: Clarify parameter names in the
 copy_xstate_to_*() methods
In-Reply-To: <20170923130016.21448-9-mingo@kernel.org>
Message-ID: <alpine.DEB.2.20.1709252145180.2418@nanos>
References: <20170923130016.21448-1-mingo@kernel.org> <20170923130016.21448-9-mingo@kernel.org>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
X-Linutronix-Spam-Score: -1.0
X-Linutronix-Spam-Level: -
X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required,  ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Sat, 23 Sep 2017, Ingo Molnar wrote:
>  static inline int
>  __copy_xstate_to_kernel(void *kbuf,
>  			const void *data,
> -			unsigned int pos, unsigned int count, int end_pos)
> +			unsigned int offset, unsigned int size, int size_total)

Why is size_total int?

>  {
> -	if (!count)
> +	if (!size)
>  		return 0;
>  
> -	if (end_pos < 0 || pos < end_pos) {
> -		unsigned int copy = end_pos < 0 ? count : min(count, end_pos - pos);
> +	if (size_total < 0 || offset < size_total) {

And why would it be < 0? The call sites of this inline are all inside of:

int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave,
    			unsigned int offset_start, int size_total)

and hand in size_total completely unmodified. copy_xstate_to_kernel()
itself has a single callsite:

int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
                unsigned int pos, unsigned int count,
                void *kbuf, void __user *ubuf)

and that hands in count unmodified.

The same issue is with the to_user() variant which is even more
obvious. All callers are inside of copy_xstate_to_user() where size_total
is an unsigned int argument which is handed in unmodified.

This signed/unsigned mismatch is confusing at best.

Thanks,

	tglx