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Message-ID: <20180118193156.GC13338@ZenIV.linux.org.uk>
Date: Thu, 18 Jan 2018 19:31:56 +0000
From: Al Viro <viro@...IV.linux.org.uk>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Network Development <netdev@...r.kernel.org>,
Dan Williams <dan.j.williams@...el.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-arch@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
Kees Cook <keescook@...omium.org>,
kernel-hardening@...ts.openwall.com,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
the arch/x86 maintainers <x86@...nel.org>,
Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Alan Cox <alan@...ux.intel.com>, David Miller <davem@...emloft.net>
Subject: Re: [RFC][PATCH] get rid of the use of set_fs() (by way of
kernel_recvmsg()) in sunrpc
On Thu, Jan 18, 2018 at 04:43:02AM +0000, Al Viro wrote:
> We could turn ->msg_control/->msg_controllen into another
> iov_iter, but seeing that we never do scatter-gather for those
> IMO that would be a massive overkill. A flag controlling whether
> ->msg_control is kernel or userland pointer would do, especially
> since we already have a flag for "do we want a native or compat
> layout for cmsg" in there.
>
> That's the only caller we need it for, but that thing looks cheap
> enough. Obviously needs to pass testing, including "is it too ugly to
> live as far as Davem is concerned" test, though...
BTW, there's another series of set_fs-removal patches in
net ioctls; still needs review, though. With that one we would be down
to 11 instances in the entire net/*:
* SO_RCVTIMEO/SO_SNDTIMEO handling in compat [sg]etsockopt()
* passing SIOC{ADD,DEL}TUNNEL down (ipmr_del_tunnel(),ipmr_new_tunnel(),
addrconf_set_dstaddr())
* SIOCGSTAMP/SIOCGSTAMPNS in compat ioctls
* SIOCADDRT/SIOCDELRT in compat ioctls
* kernel_[gs]etsockopt()
* ipv6_renew_options_kern()
I don't know if all of that stuff can be realistically done without set_fs().
kernel_setsockopt(), in particular, is unpleasant...
The patches need review and testing, obviously; I'll post them in followups,
the entire series (on top of net/master) is in
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git #work.net-ioctl
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