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Date: Sat, 13 Jan 2018 09:56:35 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Dan Williams <dan.j.williams@...el.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-arch@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	kernel-hardening@...ts.openwall.com,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Netdev <netdev@...r.kernel.org>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Elena Reshetova <elena.reshetova@...el.com>,
	Alan Cox <alan@...ux.intel.com>
Subject: Re: [PATCH v2 10/19] ipv4: prevent bounds-check bypass via
 speculative execution

On Fri, Jan 12, 2018 at 10:47:44AM -0800, Dan Williams wrote:
> On Thu, Jan 11, 2018 at 11:59 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> >> Cc: "David S. Miller" <davem@...emloft.net>
> >> Cc: Alexey Kuznetsov <kuznet@....inr.ac.ru>
> >> Cc: Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
> >> Cc: netdev@...r.kernel.org
> >> Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
> >> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> >> ---
> >>  net/ipv4/raw.c |   10 ++++++----
> >>  1 file changed, 6 insertions(+), 4 deletions(-)
> >
> > Ugh, what is this, the 4th time I've said "I don't think this is an
> > issue, so why are you changing this code." to this patch.  To be
> > followed by a "oh yeah, you are right, I'll drop it", only to see it
> > show back up in the next time this patch series is sent out?
> >
> > Same for the other patches in this series that I have reviewed 4, maybe
> > 5, times already.  The "v2" is not very true here...
> 
> The theme of the review feedback on v1 was 'don't put ifence in any
> net/ code', and that was addressed.
> 
> I honestly thought the new definition of array_ptr() changed the
> calculus on this patch. Given the same pattern appears in the ipv6
> case, and I have yet to hear that we should drop the ipv6 patch, make
> the code symmetric just for readability purposes. Otherwise we need a
> comment saying why this is safe for ipv4, but maybe not safe for ipv6,
> I think 'array_ptr' is effectively that comment. I.e. 'array_ptr()' is
> designed to be low impact for instrumenting false positives. If that
> new argument does not hold water I will definitely drop this patch.

I also argued, again in an older review of this same patch series, that
the ipv6 patch should be dropped as well for this same exact reason.

I didn't think you wanted to hear me rant about the same thing on both
patches :)

greg k-h

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