Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 30 May 2019 11:26:30 -0700 (PDT)
Message-Id: <20190530.112630.476132829981439143.davem@davemloft.net>
To:     mkubecek@suse.cz
Cc:     netdev@vger.kernel.org, vivien.didelot@gmail.com,
        linux-kernel@vger.kernel.org, kernel@savoirfairelinux.com,
        linville@redhat.com, f.fainelli@gmail.com
Subject: Re: [PATCH net-next] ethtool: copy reglen to userspace
From:   David Miller <davem@davemloft.net>
In-Reply-To: <20190530082722.GB27401@unicorn.suse.cz>
References: <20190529.221744.1136074795446305909.davem@davemloft.net>
        <20190530064848.GA27401@unicorn.suse.cz>
        <20190530082722.GB27401@unicorn.suse.cz>
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Michal Kubecek <mkubecek@suse.cz>
Date: Thu, 30 May 2019 10:27:22 +0200

> I believe this should be handled by ethtool_get_regs(), either by
> returning an error or by only copying data up to original regs.len
> passed by userspace. The former seems more correct but broken userspace
> software would suddenly start to fail where it "used to work". The
> latter would be closer to current behaviour but it would mean that
> broken userspace software might nerver notice there is something wrong.

I therefore think we need to meticulously fixup all of these adjustments
of regs.len before adjusting the copy call here in generic ethtool.