netdev - Re: [PATCH net] net: ipv6: RTF_PCPU should not be settable from userspace

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Message-ID: <CAM_iQpVOGq_ePfuTdXWharY8taHrPtW4rEeqomhZ1R8g75nXTQ@mail.gmail.com>
Date:   Thu, 20 Apr 2017 16:37:18 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     David Ahern <dsa@...ulusnetworks.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH net] net: ipv6: RTF_PCPU should not be settable from userspace

On Thu, Apr 20, 2017 at 3:43 PM, David Ahern <dsa@...ulusnetworks.com> wrote:
>
> I scanned the others. It is not clear that others should fail with
> EINVAL. Certainly a mask of unused flags can be added, but to me that is
> on top of this bug fix.
>

If we want to preserve those unused bits, we should reject them too.

RTF_PCPU is special here, it is used but only internally, so it makes
sense to silently clear it since we don't care whether people set it to
1 or 0. We should clear it for dumping too since it is internal only.