Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 5 Jun 2023 11:39:15 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Ding Hui <dinghui@sangfor.com.cn>
Cc:     Alexander Duyck <alexander.duyck@gmail.com>,
        Andrew Lunn <andrew@lunn.ch>, davem@davemloft.net,
        edumazet@google.com, pabeni@redhat.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, pengdonglin@sangfor.com.cn,
        huangcun@sangfor.com.cn
Subject: Re: [PATCH net-next] net: ethtool: Fix out-of-bounds copy to user
Message-ID: <20230605113915.4258af7f@kernel.org>
In-Reply-To: <f6ad6281-df30-93cf-d057-5841b8c1e2e6@sangfor.com.cn>
References: <20230601112839.13799-1-dinghui@sangfor.com.cn>
        <135a45b2c388fbaf9db4620cb01b95230709b9ac.camel@gmail.com>
        <eed0cbf7-ff12-057e-e133-0ddf5e98ef68@sangfor.com.cn>
        <6110cf9f-c10e-4b9b-934d-8d202b7f5794@lunn.ch>
        <f7e23fe6-4d30-ef1b-a431-3ef6ec6f77ba@sangfor.com.cn>
        <6e28cea9-d615-449d-9c68-aa155efc8444@lunn.ch>
        <CAKgT0UdyykQL-BidjaNpjX99FwJTxET51U29q4_CDqmABUuVbw@mail.gmail.com>
        <ece228a3-5c31-4390-b6ba-ec3f2b6c5dcb@lunn.ch>
        <CAKgT0Uf+XaKCFgBRTn-viVsKkNE7piAuDpht=efixsAV=3JdFQ@mail.gmail.com>
        <44905acd-3ac4-cfe5-5e91-d182c1959407@sangfor.com.cn>
        <20230602225519.66c2c987@kernel.org>
        <5f0f2bab-ae36-8b13-2c6d-c69c6ff4a43f@sangfor.com.cn>
        <20230604104718.4bf45faf@kernel.org>
        <f6ad6281-df30-93cf-d057-5841b8c1e2e6@sangfor.com.cn>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Mon, 5 Jun 2023 11:39:59 +0800 Ding Hui wrote:
> Case 1:
> If the user len/n_stats is not zero, we will treat it as correct usage
> (although we cannot distinguish between the real correct usage and
> uninitialized usage). Return -EINVAL if current length exceed the one
> user specified.

This assumes user will zero-initialize the value rather than do
something like:

	buf = malloc(1 << 16); // 64k should always be enough
	ioctl(s, ETHTOOL_GSTATS, buf)

	for (i = 0; i < buf.n_stats; i++)
		/* use stats */

:(

> Case 2:
> If it is zero, we will treat it as incorrect usage, we can add a
> pr_err_once() for it and keep to be compatible with it for a period of time.
> At a suitable time in the future, this part can be removed by maintainers.