From: Tim Chen <tim.c.chen@linux.intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>,
arjan@linux.intel.com, tglx@linutronix.de, karahmed@amazon.de,
x86@kernel.org, linux-kernel@vger.kernel.org,
peterz@infradead.org, pbonzini@redhat.com, ak@linux.intel.com,
torvalds@linux-foundation.org, gregkh@linux-foundation.org,
mingo@kernel.org, luto@kernel.org, linux@dominikbrodowski.net
Subject: Re: [PATCH] x86/speculation: Use Indirect Branch Prediction Barrier in context switch
Date: Tue, 30 Jan 2018 16:25:26 -0800 [thread overview]
Message-ID: <74fd9c82-cd18-562b-8df6-69f629da460b@linux.intel.com> (raw)
In-Reply-To: <20180130224340.2zdfqttupugtqww5@pd.tnic>
On 01/30/2018 02:43 PM, Borislav Petkov wrote:
> On Tue, Jan 30, 2018 at 02:26:53PM -0800, Tim Chen wrote:
>> If the process has multiple threads running on different cpus,
>
> I'm talking about issuing the barrier in set_dumpable(). What threads on
> multiple CPUs?
>
As dumpable is a property in mm->flags, it affects all threads running on other cpus sharing
the same mm. If you issue IBPB only on the cpu that perform the set_dumpable(),
the theoretical hole you are trying to close still exist on threads running on
other cpu.
time ----->
(cpu A) set_dumpable victim (thread1), issue IBPB
(cpu B) attacker -> victim (thread2), missed IBPB -> attacker -> victim (IBPB issued)
That said, I think the risk is minuscule and is not worth the cost to set IBPB on the other cpus.
Tim
next prev parent reply other threads:[~2018-01-31 0:25 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-29 22:04 David Woodhouse
2018-01-30 17:48 ` Josh Poimboeuf
2018-01-30 21:23 ` Tim Chen
2018-01-30 22:00 ` Borislav Petkov
2018-01-30 22:21 ` Thomas Gleixner
2018-01-30 22:55 ` Borislav Petkov
2018-01-31 3:59 ` Josh Poimboeuf
2018-01-31 23:25 ` Tim Chen
2018-01-30 20:38 ` Borislav Petkov
2018-01-30 21:03 ` Tim Chen
2018-01-30 21:57 ` Borislav Petkov
2018-01-30 22:26 ` Tim Chen
2018-01-30 22:43 ` Borislav Petkov
2018-01-31 0:25 ` Tim Chen [this message]
2018-01-31 0:41 ` Borislav Petkov
2018-01-30 22:39 ` [tip:x86/pti] " tip-bot for Tim Chen
2018-01-31 7:03 ` Dominik Brodowski
2018-01-31 13:24 ` Josh Poimboeuf
2018-02-01 8:25 ` Christian Brauner
2018-02-01 8:31 ` David Woodhouse
2018-02-01 15:40 ` Josh Poimboeuf
2018-02-04 19:39 ` Dominik Brodowski
2018-02-05 14:18 ` David Woodhouse
2018-02-05 19:35 ` Tim Chen
-- strict thread matches above, loose matches on Subject: below --
2018-01-29 11:33 [PATCH] " David Woodhouse
2018-01-29 12:28 ` Dominik Brodowski
2018-01-29 12:44 ` David Woodhouse
2018-01-29 13:56 ` Dominik Brodowski
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