From: Laura Abbott <labbott@redhat.com>
To: Kees Cook <keescook@chromium.org>
Cc: "kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
"David S. Miller" <davem@davemloft.net>,
Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
Jiri Slaby <jslaby@suse.cz>, Guenter Roeck <linux@roeck-us.net>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/5] lkdtm: add function for testing .rodata section
Date: Thu, 9 Jun 2016 18:14:36 -0700 [thread overview]
Message-ID: <0fdbafc6-21ce-636c-038c-1e870ebf75d6@redhat.com> (raw)
In-Reply-To: <CAGXu5jJTx3gzzXSNK5x+ui0x7kGhvrV8vhKVoc33T2W3h4T5XQ@mail.gmail.com>
On 06/08/2016 02:26 PM, Kees Cook wrote:
> On Wed, Jun 8, 2016 at 8:46 AM, Kees Cook <keescook@chromium.org> wrote:
>> On Tue, Jun 7, 2016 at 6:02 PM, Laura Abbott <labbott@redhat.com> wrote:
>>> On 06/07/2016 02:57 PM, Kees Cook wrote:
>>>>
>>>> This adds a function that lives in the .rodata section. The section
>>>> flags are corrected using objcopy since there is no way with gcc to
>>>> declare section flags in an architecture-agnostic way.
>>>>
>>>
>>> Permit me to be the bearer of bad architecture news once again. With
>>> arm64 cross compiler (both Fedora 6.1.1 and Linaro 5.1)
>>>
>>> CC drivers/misc/lkdtm_rodata.o
>>> OBJCOPY drivers/misc/lkdtm_rodata_objcopy.o
>>> LD drivers/misc/lkdtm.o
>>> drivers/misc/lkdtm_rodata_objcopy.o: file not recognized: File format not
>>> recognized
>>> scripts/Makefile.build:423: recipe for target 'drivers/misc/lkdtm.o' failed
>>> make[2]: *** [drivers/misc/lkdtm.o] Error 1
>>> scripts/Makefile.build:440: recipe for target 'drivers/misc' failed
>>> make[1]: *** [drivers/misc] Error 2
>>> Makefile:985: recipe for target 'drivers' failed
>>> make: *** [drivers] Error 2
>>>
>>>
>>> As far as I can tell this is because arm64 defines OBJCOPYFLAGS and they get
>>> propagated to objcopy
>>>
>>> aarch64-linux-gnu-objcopy -O binary -R .note -R .note.gnu.build-id -R
>>> .comment
>>> -S --set-section-flags .text=alloc,readonly
>>> --rename-section .text=.rodata drivers/misc/lkdtm_rodata.o
>>> drivers/misc/lkdtm_rodata_objcopy.o
>>>
>>> vs x86
>>>
>>> objcopy --set-section-flags .text=alloc,readonly --rename-section
>>> .text=.rodata
>>> drivers/misc/lkdtm_rodata.o drivers/misc/lkdtm_rodata_objcopy.o
>>>
>>>
>>> specifically it's the -O binary that seems to break things, the same failure
>>> happens on x86 as well with the the same commands. It works if I clear out
>>> the OBJCOPYFLAGS variable first but I don't think that's the correct way to
>>> fix this.
>>>
>>> Thanks,
>>> Laura
>>>
>>>
>>>> Signed-off-by: Kees Cook <keescook@chromium.org>
>>>> ---
>>>> drivers/misc/Makefile | 7 +++++++
>>>> drivers/misc/lkdtm.h | 6 ++++++
>>>> drivers/misc/lkdtm_core.c | 24 +++++++++++++++++-------
>>>> drivers/misc/lkdtm_rodata.c | 10 ++++++++++
>>>> 4 files changed, 40 insertions(+), 7 deletions(-)
>>>> create mode 100644 drivers/misc/lkdtm.h
>>>> create mode 100644 drivers/misc/lkdtm_rodata.c
>>>>
>>>> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
>>>> index c3cb6ad8cc37..b2d3d68dfa22 100644
>>>> --- a/drivers/misc/Makefile
>>>> +++ b/drivers/misc/Makefile
>>>> @@ -59,3 +59,10 @@ obj-$(CONFIG_CXL_BASE) += cxl/
>>>> obj-$(CONFIG_PANEL) += panel.o
>>>>
>>>> lkdtm-$(CONFIG_LKDTM) += lkdtm_core.o
>>>> +lkdtm-$(CONFIG_LKDTM) += lkdtm_rodata_objcopy.o
>>>> +
>
> If I add:
>
> OBJCOPYFLAGS :=
>
> here, it seems to fix things...
>
I can confirm that this works on arm64
# echo EXEC_RODATA > /sys/kernel/debug/provoke-crash/DIRECT
[ 21.725514] lkdtm: Performing direct entry EXEC_RODATA
[ 21.725890] lkdtm: attempting ok execution at ffff0000084c0e08
[ 21.726030] lkdtm: attempting bad execution at ffff000008880700
[ 21.726401] Bad mode in Synchronous Abort handler detected on CPU2, code 0x8400000e -- IABT (current EL)
[ 21.726847] CPU: 2 PID: 998 Comm: sh Not tainted 4.7.0-rc2+ #13
I wish the exception was clearer what the actual error was. I might propose a
patch to make it more obvious.
Thanks,
Laura
next prev parent reply other threads:[~2016-06-10 1:14 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-07 21:57 [PATCH 0/5] lkdtm: add usercopy and rodata, fix atomic Kees Cook
2016-06-07 21:57 ` [PATCH 1/5] lkdtm: split build into multiple source files Kees Cook
2016-06-07 21:57 ` [PATCH 2/5] lkdtm: clean up after rename Kees Cook
2016-06-07 21:57 ` [PATCH 3/5] lkdtm: add function for testing .rodata section Kees Cook
2016-06-08 1:02 ` Laura Abbott
2016-06-08 15:46 ` Kees Cook
2016-06-08 16:15 ` Laura Abbott
2016-06-08 21:26 ` Kees Cook
2016-06-10 1:14 ` Laura Abbott [this message]
[not found] ` <87h9b4oebf.fsf@concordia.ellerman.id.au>
2016-08-01 19:45 ` Linker segfault on powerpc when CONFIG_LKDTM=y (was Re: [kernel-hardening] [PATCH 3/5] lkdtm: add function for testing .rodata section) Kees Cook
2016-08-02 3:12 ` [kernel-hardening] " Michael Ellerman
2016-08-02 19:12 ` Kees Cook
2016-08-03 4:46 ` Michael Ellerman
2016-06-07 21:57 ` [PATCH 4/5] lkdtm: add usercopy tests Kees Cook
2016-06-07 23:36 ` kbuild test robot
2016-06-08 0:07 ` kbuild test robot
2016-06-07 21:57 ` [PATCH 5/5] lkdtm: split atomic test into over and underflow 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=0fdbafc6-21ce-636c-038c-1e870ebf75d6@redhat.com \
--to=labbott@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=davem@davemloft.net \
--cc=gregkh@linuxfoundation.org \
--cc=jslaby@suse.cz \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@roeck-us.net \
--cc=mchehab@osg.samsung.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
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;
as well as URLs for NNTP newsgroup(s).