linux-kernel - Re: [PATCH v2 1/3] x86/ldt: Make modify

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Message-ID: <CAMzpN2g5BHZaEeW0SVuny_ReHKj=+s6BZW6-RGQRe6FeU8_3Ew@mail.gmail.com>
Date:	Tue, 21 Jul 2015 22:01:05 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	Andy Lutomirski <luto@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"security@...nel.org" <security@...nel.org>,
	X86 ML <x86@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Sasha Levin <sasha.levin@...cle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	stable <stable@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] x86/ldt: Make modify_ldt synchronous

On Tue, Jul 21, 2015 at 3:59 PM, Andy Lutomirski <luto@...nel.org> wrote:
> modify_ldt has questionable locking and does not synchronize
> threads.  Improve it: redesign the locking and synchronize all
> threads' LDTs using an IPI on all modifications.

What does this fix?  I can see sending an IPI if the LDT is
reallocated, but on every update seems unnecessary.

--
Brian Gerst
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