From: "H. Peter Anvin" <hpa@zytor.com>
To: peterz@infradead.org, brgerst@gmail.com, mingo@kernel.org,
tglx@linutronix.de, torvalds@linux-foundation.org,
luto@kernel.org, linux-kernel@vger.kernel.org,
luto@amacapital.net, bp@alien8.de, dvlasenk@redhat.com,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/urgent] x86/entry/32: Add an ASM_CLAC to entry_SYSENTER_32
Date: Wed, 24 Feb 2016 22:00:55 -0800 [thread overview]
Message-ID: <56CE9897.6080702@zytor.com> (raw)
In-Reply-To: <tip-04d1d281dcfe683a53cddfab8371fc8bb302b069@git.kernel.org>
On 02/24/16 21:53, tip-bot for Andy Lutomirski wrote:
> Commit-ID: 04d1d281dcfe683a53cddfab8371fc8bb302b069
> Gitweb: http://git.kernel.org/tip/04d1d281dcfe683a53cddfab8371fc8bb302b069
> Author: Andy Lutomirski <luto@kernel.org>
> AuthorDate: Tue, 23 Feb 2016 13:19:29 -0800
> Committer: Ingo Molnar <mingo@kernel.org>
> CommitDate: Wed, 24 Feb 2016 08:43:04 +0100
>
> x86/entry/32: Add an ASM_CLAC to entry_SYSENTER_32
>
> Both before and after 5f310f739b4c ("x86/entry/32: Re-implement
> SYSENTER using the new C path"), we relied on a uaccess very early
> in the SYSENTER path to clear AC. After that change, though, we can
> potentially make it all the way into C code with AC set, which
> enlarges the attack surface for SMAP bypass by doing SYSENTER with
> AC set.
>
> Strengthen the SMAP protection by addding the missing ASM_CLAC right
> at the beginning.
>
Hmmm... this potentially adds a *lot* of unnecessary cycles to this
path. Could we reinstate the early uaccess?
-hpa
next prev parent reply other threads:[~2016-02-25 6:27 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-23 21:19 [PATCH] x86/entry/32: Add an ASM_CLAC to entry_SYSENTER_32 Andy Lutomirski
2016-02-24 15:46 ` Brian Gerst
2016-02-24 16:56 ` Andy Lutomirski
2016-02-25 5:53 ` [tip:x86/urgent] " tip-bot for Andy Lutomirski
2016-02-25 6:00 ` H. Peter Anvin [this message]
2016-02-25 8:07 ` Andy Lutomirski
2016-02-25 8:11 ` Andy Lutomirski
2016-02-25 8:14 ` Ingo Molnar
2016-02-25 8:29 ` Mike Galbraith
2016-02-25 8:40 ` Ingo Molnar
2016-02-25 9:08 ` Mike Galbraith
[not found] ` <CALCETrWqCnhxvQ5qNp_O_7K7KW1H3FmHiX=mp+C5oeBEx=3YVA@mail.gmail.com>
2016-02-25 13:47 ` Brian Gerst
2016-02-25 15:42 ` Brian Gerst
2016-02-25 18:20 ` Andy Lutomirski
2016-02-25 18:30 ` Linus Torvalds
2016-02-25 18:40 ` Andy Lutomirski
2016-02-25 19:31 ` Brian Gerst
2016-02-25 19:39 ` Andy Lutomirski
2016-02-25 19:49 ` Brian Gerst
2016-02-25 19:52 ` Andy Lutomirski
2016-02-25 20:54 ` Linus Torvalds
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