From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Brian Gerst <brgerst@gmail.com>
Subject: Re: [PATCH 02/10] x86/entry/compat: In SYSENTER, sink AC clearing below the existing FLAGS test
Date: Mon, 29 Feb 2016 23:09:03 +0100 [thread overview]
Message-ID: <20160229220903.GH3724@pd.tnic> (raw)
In-Reply-To: <CALCETrVfY73Q2SLG9-f4JB_L5nHfc8Epfydwk5=5xY3EC3dtuA@mail.gmail.com>
On Mon, Feb 29, 2016 at 12:45:58PM -0800, Andy Lutomirski wrote:
> I don't think so. Sensible user programs shouldn't set AC in the first place.
Then I'm most likely missing something: so before this patch, we did
unconditionally CLAC thus disallowing kernel access to user pages. Why
don't we need it anymore and need to pay attention only to user rFLAGS?
Especially since we do:
do_fast_syscall_32
|-> __get_user
|-> __get_user_nocheck
|-> __uaccess_begin which is stac()
Or are we saying, we don't need that CLAC in the beginning of
entry_SYSENTER_compat() at all because we're going to STAC anyway in
__get_user() ?
Hmmm...
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
next prev parent reply other threads:[~2016-02-29 22:09 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-29 5:28 [PATCH 00/10] x86: Various SYSENTER/SYSEXIT/#DB fixes and cleanups Andy Lutomirski
2016-02-29 5:28 ` [PATCH 01/10] selftests/x86: In syscall_nt, test NT|TF as well Andy Lutomirski
2016-03-02 12:59 ` Borislav Petkov
2016-03-02 14:01 ` One Thousand Gnomes
2016-03-02 14:28 ` Borislav Petkov
2016-03-02 19:03 ` Andy Lutomirski
2016-03-02 19:30 ` Borislav Petkov
2016-02-29 5:28 ` [PATCH 02/10] x86/entry/compat: In SYSENTER, sink AC clearing below the existing FLAGS test Andy Lutomirski
2016-02-29 20:39 ` Borislav Petkov
2016-02-29 20:45 ` Andy Lutomirski
2016-02-29 22:09 ` Borislav Petkov [this message]
2016-02-29 22:33 ` Brian Gerst
2016-02-29 22:37 ` Borislav Petkov
2016-02-29 5:28 ` [PATCH 03/10] x86/entry/32: Filter NT and speed up AC filtering in SYSENTER Andy Lutomirski
2016-03-02 13:24 ` Borislav Petkov
2016-02-29 5:28 ` [PATCH 04/10] x86/entry/32: Restore FLAGS on SYSEXIT Andy Lutomirski
2016-02-29 5:28 ` [PATCH 05/10] x86/traps: Clear TIF_BLOCKSTEP on all debug exceptions Andy Lutomirski
2016-02-29 5:28 ` [PATCH 06/10] x86/traps: Clear DR6 early in do_debug and improve the comment Andy Lutomirski
2016-02-29 5:28 ` [PATCH 07/10] x86/entry: Vastly simplify SYSENTER TF handling Andy Lutomirski
2016-02-29 5:28 ` [PATCH 08/10] x86/entry: Only allocate space for SYSENTER_stack if needed Andy Lutomirski
2016-02-29 5:28 ` [PATCH 09/10] x86/entry/32: Simplify and fix up the SYSENTER stack #DB/NMI fixup Andy Lutomirski
2016-02-29 5:28 ` [PATCH 10/10] x86/entry/32: Add and check a stack canary for the SYSENTER stack Andy Lutomirski
2016-02-29 18:55 ` [PATCH 00/10] x86: Various SYSENTER/SYSEXIT/#DB fixes and cleanups Andy Lutomirski
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