From: Andy Lutomirski <luto@amacapital.net>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: "security@kernel.org" <security@kernel.org>,
Jan Beulich <jbeulich@suse.com>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Cooper <andrew.cooper3@citrix.com>,
X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
xen-devel <xen-devel@lists.xen.org>,
Borislav Petkov <bp@alien8.de>, stable <stable@vger.kernel.org>,
Andy Lutomirski <luto@kernel.org>,
Sasha Levin <sasha.levin@oracle.com>
Subject: Re: [PATCH v3 1/3] x86/ldt: Make modify_ldt synchronous
Date: Fri, 24 Jul 2015 21:58:23 -0700 [thread overview]
Message-ID: <CALCETrVwtMv58+AZuQhLxykDp6VYSwO5SnYRiKWqTMkvORSFJA__17368.0641259581$1437800398$gmane$org@mail.gmail.com> (raw)
In-Reply-To: <55B30CE3.2010902@oracle.com>
On Fri, Jul 24, 2015 at 9:13 PM, Boris Ostrovsky
<boris.ostrovsky@oracle.com> wrote:
>
>
> On 07/22/2015 06:20 PM, Boris Ostrovsky wrote:
>>
>> On 07/22/2015 03:23 PM, Andy Lutomirski wrote:
>>>
>>>
>>> + error = -ENOMEM;
>>> + new_ldt = alloc_ldt_struct(newsize);
>>> + if (!new_ldt)
>>> goto out_unlock;
>>> - }
>>> - fill_ldt(&ldt, &ldt_info);
>>> - if (oldmode)
>>> - ldt.avl = 0;
>>> + if (old_ldt) {
>>> + memcpy(new_ldt->entries, old_ldt->entries,
>>> + oldsize * LDT_ENTRY_SIZE);
>>> + }
>>> + memset(new_ldt->entries + oldsize * LDT_ENTRY_SIZE, 0,
>>> + (newsize - oldsize) * LDT_ENTRY_SIZE);
>>
>>
>> We need to zero out full page (probably better in alloc_ldt_struct() with
>> vmzalloc/__GFP_ZERO) --- Xen checks whole page that is assigned to G/LDT
>> and gets unhappy if an invalid descriptor is found there.
>>
>> This fixes one problem. There is something else that Xen gets upset about,
>> I haven't figured what it is yet (and I am out tomorrow so it may need to
>> wait until Friday).
>>
>
>
> What I thought was another problem turned out not to be one so both 64- and
> 32-bit tests passed on 64-bit PV (when allocated LDT is zeroed out)
>
> However, on 32-bit kernel the test is failing multicpu test, I don't know
> yet what it is.
Test case bug or unrelated kernel bug depending on your point of view.
I forgot that x86_32 and x86_64 have very different handling of IRET
faults. Wait for v2 :)
--Andy
next prev parent reply other threads:[~2015-07-25 4:58 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1437592883.git.luto@kernel.org>
2015-07-22 19:23 ` [PATCH v3 1/3] x86/ldt: Make modify_ldt synchronous Andy Lutomirski
2015-07-22 19:23 ` [PATCH v3 2/3] x86/ldt: Make modify_ldt optional Andy Lutomirski
2015-07-22 19:23 ` [PATCH v3 3/3] selftests/x86, x86/ldt: Add a selftest for modify_ldt Andy Lutomirski
[not found] ` <7bfde005b84a90a83bf668a320c7d4ad1b940065.1437592883.git.luto@kernel.org>
2015-07-23 7:13 ` [PATCH v3 2/3] x86/ldt: Make modify_ldt optional Jan Beulich
2015-07-23 10:24 ` Willy Tarreau
[not found] ` <20150723102434.GA2929@1wt.eu>
2015-07-23 23:36 ` Kees Cook
[not found] ` <CAGXu5j+yEWLuxJ9JUGyN7BxME+iOVXfpFgrZ-_2WXUn6A=0dVg@mail.gmail.com>
2015-07-23 23:40 ` Andy Lutomirski
[not found] ` <CALCETrVvfA+_N_tU2LUwvh+2Q_4AExbQkSgW1C4tESAvhY+4Dg@mail.gmail.com>
2015-07-23 23:58 ` Willy Tarreau
[not found] ` <20150723235805.GA3191@1wt.eu>
2015-07-24 0:09 ` Kees Cook
[not found] ` <CAGXu5jJNfMvvdr0q17nBz+HiEJuFa7Kvo=ZPAnb4E7So4W0QOA@mail.gmail.com>
2015-07-24 7:24 ` Willy Tarreau
[not found] ` <20150724072451.GB3293@1wt.eu>
2015-07-24 7:48 ` Willy Tarreau
[not found] ` <049fdbab8ae2ecac1c8b40ecd558e9df45ccd5d3.1437592883.git.luto@kernel.org>
2015-07-22 22:20 ` [PATCH v3 1/3] x86/ldt: Make modify_ldt synchronous Boris Ostrovsky
2015-07-24 6:37 ` Borislav Petkov
2015-07-24 15:29 ` Borislav Petkov
[not found] ` <55B01745.4010702@oracle.com>
2015-07-25 4:13 ` Boris Ostrovsky
[not found] ` <55B30CE3.2010902@oracle.com>
2015-07-25 4:58 ` Andy Lutomirski [this message]
[not found] ` <20150724152955.GC21441@nazgul.tnic>
2015-07-25 4:52 ` Andy Lutomirski
[not found] ` <CALCETrX=uGdTfmz7KkbVyMKEmwcS4C43L5eNsy65VjNsL=7KJA@mail.gmail.com>
2015-07-25 8:37 ` Borislav Petkov
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