From: borntraeger@de•ibm.com (Christian Borntraeger)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v3 02/11] mm: Hardened usercopy
Date: Tue, 19 Jul 2016 22:44:58 +0200 [thread overview]
Message-ID: <578E914A.7070900@de.ibm.com> (raw)
In-Reply-To: <CAGXu5j+HqLY1gZycV9S9_Vf8uuQj4Z3qsV8WBxLORuseiJaw5Q@mail.gmail.com>
On 07/19/2016 10:34 PM, Kees Cook wrote:
[...]
>>
>> So what about for the CONFIG text:
>>
>> An architecture should select this if the kernel mapping has a secondary
>> linear mapping of the kernel text - in other words more than one virtual
>> kernel address that points to the kernel image. This is used to verify
>> that kernel text exposures are not visible under CONFIG_HARDENED_USERCOPY.
>
> Sounds good, I've adjusted it for now.
>
>>> I wonder if I can avoid the CONFIG entirely if I just did a
>>> __va(__pa(_stext)) != _stext test... would that break anyone?
>>
>> Can this be resolved on all platforms at compile time?
>
> Well, I think it still needs a runtime check (compile-time may not be
> able to tell about kaslr, or who knows what else). I would really like
> to avoid the CONFIG if possible, though. Would this do the right thing
> on s390? This appears to work where I'm able to test it (32/64 x86,
> 32/64 arm):
>
> unsigned long textlow = (unsigned long)_stext;
> unsigned long texthigh = (unsigned long)_etext;
> unsigned long textlow_linear = (unsigned long)__va(__pa(textlow);
> unsigned long texthigh_linear = (unsigned long)__va(__pa(texthigh);
>
as we have
#define PAGE_OFFSET 0x0UL
#define __pa(x) (unsigned long)(x)
#define __va(x) (void *)(unsigned long)(x)
both should be identical on s390 as of today, so it should work fine and only
do the check once
> if (overlaps(ptr, n, textlow, texthigh))
> return "<kernel text>";
>
> /* Check against possible secondary linear mapping as well. */
> if (textlow != textlow_linear &&
> overlaps(ptr, n, textlow_linear, texthigh_linear))
> return "<linear kernel text>";
>
> return NULL;
>
>
> -Kees
>
PS: Not sure how useful and flexible this offers is but you can get some temporary
free access to an s390 on https://developer.ibm.com/linuxone/
next prev parent reply other threads:[~2016-07-19 20:44 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-15 21:44 [PATCH v3 00/11] mm: Hardened usercopy Kees Cook
2016-07-15 21:44 ` [PATCH v3 01/11] mm: Implement stack frame object validation Kees Cook
2016-07-15 21:44 ` [PATCH v3 02/11] mm: Hardened usercopy Kees Cook
2016-07-19 1:06 ` Laura Abbott
2016-07-19 18:48 ` Kees Cook
2016-07-19 22:00 ` [PATCH] mm: Add is_migrate_cma_page Laura Abbott
2016-07-19 22:40 ` Kees Cook
2016-07-20 10:24 ` [PATCH v3 02/11] mm: Hardened usercopy Balbir Singh
2016-07-20 15:36 ` Laura Abbott
2016-07-19 1:52 ` Laura Abbott
2016-07-19 19:12 ` Kees Cook
2016-07-19 22:55 ` Kees Cook
2016-07-19 9:21 ` Christian Borntraeger
2016-07-19 19:31 ` Kees Cook
2016-07-19 20:14 ` Christian Borntraeger
2016-07-19 20:34 ` Kees Cook
2016-07-19 20:44 ` Christian Borntraeger [this message]
2016-07-21 6:52 ` Michael Ellerman
[not found] ` <5790711f.2350420a.b4287.2cc0SMTPIN_ADDED_BROKEN@mx.google.com>
2016-07-21 18:34 ` Kees Cook
2016-07-22 17:45 ` Josh Poimboeuf
2016-07-25 9:27 ` David Laight
2016-07-26 2:09 ` Michael Ellerman
[not found] ` <87poq1jgtw.fsf@concordia.ellerman.id.au>
2016-07-26 4:46 ` Kees Cook
2016-07-15 21:44 ` [PATCH v3 03/11] x86/uaccess: Enable hardened usercopy Kees Cook
2016-07-15 21:44 ` [PATCH v3 04/11] ARM: uaccess: " Kees Cook
2016-07-15 21:44 ` [PATCH v3 05/11] arm64/uaccess: " Kees Cook
2016-07-15 21:44 ` [PATCH v3 06/11] ia64/uaccess: " Kees Cook
2016-07-15 21:44 ` [PATCH v3 07/11] powerpc/uaccess: " Kees Cook
2016-07-15 21:44 ` [PATCH v3 08/11] sparc/uaccess: " Kees Cook
2016-07-15 21:44 ` [PATCH v3 09/11] s390/uaccess: " Kees Cook
2016-07-15 21:44 ` [PATCH v3 10/11] mm: SLAB hardened usercopy support Kees Cook
2016-07-15 21:44 ` [PATCH v3 11/11] mm: SLUB " Kees Cook
2016-07-18 8:26 ` [PATCH v3 00/11] mm: Hardened usercopy Balbir Singh
2016-07-20 9:52 ` David Laight
2016-07-20 15:31 ` Kees Cook
2016-07-20 16:02 ` David Laight
2016-07-20 16:22 ` Rik van Riel
2016-07-20 17:44 ` Kees Cook
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=578E914A.7070900@de.ibm.com \
--to=borntraeger@de$(echo .)ibm.com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox