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 S1758824AbdJQEcu (ORCPT <rfc822;w@1wt.eu>);
        Tue, 17 Oct 2017 00:32:50 -0400
Received: from mail-pf0-f182.google.com ([209.85.192.182]:52013 "EHLO
        mail-pf0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1758385AbdJQEct (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 17 Oct 2017 00:32:49 -0400
X-Google-Smtp-Source: AOwi7QCUXo0ASDtmaBTIophduK96wxrgb0e9FuVDSrL5gCmkEbY/vJz5PoHXVroKQYRgmkxhzONIOQ==
Subject: Re: [PATCH] bpf: devmap: Check attr->max_entries more carefully
To: Richard Weinberger <richard@nod.at>, netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, daniel@iogearbox.net, ast@kernel.org,
        sp3485@columbia.edu
References: <20171015220020.8157-1-richard@nod.at>
 <100542240.i6NpMmsy5C@blindfold>
From: John Fastabend <john.fastabend@gmail.com>
Message-ID: <0b5e4a49-3738-5b57-1abf-1912b2afff2c@gmail.com>
Date: Mon, 16 Oct 2017 21:30:38 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.3.0
MIME-Version: 1.0
In-Reply-To: <100542240.i6NpMmsy5C@blindfold>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 10/15/2017 03:13 PM, Richard Weinberger wrote:
> Am Montag, 16. Oktober 2017, 00:00:20 CEST schrieb Richard Weinberger:
>> max_entries is user controlled and used as input for __alloc_percpu().
>> This function expects that the allocation size is a power of two and
>> less than PCPU_MIN_UNIT_SIZE.
>> Otherwise a WARN() is triggered.
> 
> On a second though, I think we should also have a hard limit for ->max_entries 
> or check for an overflow here:
> 

Or just,

static u64 dev_map_bitmap_size(const union bpf_attr *attr)
{
	return BITS_TO_LONGS((u64) attr->max_entries) *
		sizeof(unsigned long);
}

Let me know if you want me to send a patch or if you want to.

Thanks,
John

> static u64 dev_map_bitmap_size(const union bpf_attr *attr)
> {
>         return BITS_TO_LONGS(attr->max_entries) * sizeof(unsigned long);
> }
> 
> Thanks,
> //richard
>