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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 17 Jan 2018 19:16:02 -0800
Message-ID: <CA+55aFzKPed+89wz=ajWNpsQ8Kh+AQWx61hwVqqDh7_=h4tecg@mail.gmail.com>
Subject: Re: [RFC][PATCH] get rid of the use of set_fs() (by way of
 kernel_recvmsg()) in sunrpc
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Network Development <netdev@vger.kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arch@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
        Kees Cook <keescook@chromium.org>,
        kernel-hardening@lists.openwall.com,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alan Cox <alan@linux.intel.com>,
        David Miller <davem@davemloft.net>
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On Wed, Jan 17, 2018 at 7:06 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> Similar to the way put_cmsg() handles 32bit case on biarch
> targets, introduce a flag telling put_cmsg() to treat
> ->msg_control as kernel pointer, using memcpy instead of
> copy_to_user().  That allows to avoid the use of kernel_recvmsg()
> with its set_fs().

If this is the only case that kernel_recvmsg() exists for, then by all
means, that patch certainly looks like a good thing.

                 Linus