* [PATCH] arm64: mm: Mark .rodata as RO
@ 2016-02-12 16:13 Jeremy Linton
2016-02-12 18:25 ` Mark Rutland
0 siblings, 1 reply; 5+ messages in thread
From: Jeremy Linton @ 2016-02-12 16:13 UTC (permalink / raw)
To: linux-arm-kernel
Currently the .rodata section is actually still executable when DEBUG_RODATA
is enabled. This changes that so the .rodata is actually read only, no execute.
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
---
arch/arm64/kernel/vmlinux.lds.S | 5 +++--
arch/arm64/mm/mmu.c | 14 +++++++++++---
2 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index ab4e436..2e2c053 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -114,8 +114,9 @@ SECTIONS
*(.got) /* Global offset table */
}
- RO_DATA(PAGE_SIZE)
- EXCEPTION_TABLE(8)
+ ALIGN_DEBUG_RO_MIN(0)
+ RO_DATA(PAGE_SIZE) /* everything from this point to */
+ EXCEPTION_TABLE(8) /* _etext will be marked RO NX */
NOTES
ALIGN_DEBUG_RO_MIN(PAGE_SIZE)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index ab69a99..a3f4112 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -453,10 +453,18 @@ static void __init map_mem(pgd_t *pgd)
#ifdef CONFIG_DEBUG_RODATA
void mark_rodata_ro(void)
{
- create_mapping_late(__pa(_stext), (unsigned long)_stext,
- (unsigned long)_etext - (unsigned long)_stext,
- PAGE_KERNEL_ROX);
+ unsigned long section_size;
+ section_size = (unsigned long)__start_rodata - (unsigned long)_stext;
+ create_mapping_late(__pa(_stext), (unsigned long)_stext,
+ section_size, PAGE_KERNEL_ROX);
+ /*
+ * mark .rodata as read only. Use _etext rather than __end_rodata to
+ * cover NOTES and EXCEPTION_TABLE.
+ */
+ section_size = (unsigned long)_etext - (unsigned long)__start_rodata;
+ create_mapping_late(__pa(__start_rodata), (unsigned long)__start_rodata,
+ section_size, PAGE_KERNEL_RO);
}
#endif
--
2.4.3
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH] arm64: mm: Mark .rodata as RO
2016-02-12 16:13 [PATCH] arm64: mm: Mark .rodata as RO Jeremy Linton
@ 2016-02-12 18:25 ` Mark Rutland
2016-02-16 18:10 ` Kees Cook
0 siblings, 1 reply; 5+ messages in thread
From: Mark Rutland @ 2016-02-12 18:25 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, Feb 12, 2016 at 10:13:19AM -0600, Jeremy Linton wrote:
> Currently the .rodata section is actually still executable when DEBUG_RODATA
> is enabled. This changes that so the .rodata is actually read only, no execute.
>
> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
> ---
> arch/arm64/kernel/vmlinux.lds.S | 5 +++--
> arch/arm64/mm/mmu.c | 14 +++++++++++---
> 2 files changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> index ab4e436..2e2c053 100644
> --- a/arch/arm64/kernel/vmlinux.lds.S
> +++ b/arch/arm64/kernel/vmlinux.lds.S
> @@ -114,8 +114,9 @@ SECTIONS
> *(.got) /* Global offset table */
> }
>
> - RO_DATA(PAGE_SIZE)
> - EXCEPTION_TABLE(8)
> + ALIGN_DEBUG_RO_MIN(0)
> + RO_DATA(PAGE_SIZE) /* everything from this point to */
> + EXCEPTION_TABLE(8) /* _etext will be marked RO NX */
> NOTES
>
> ALIGN_DEBUG_RO_MIN(PAGE_SIZE)
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index ab69a99..a3f4112 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -453,10 +453,18 @@ static void __init map_mem(pgd_t *pgd)
> #ifdef CONFIG_DEBUG_RODATA
> void mark_rodata_ro(void)
> {
> - create_mapping_late(__pa(_stext), (unsigned long)_stext,
> - (unsigned long)_etext - (unsigned long)_stext,
> - PAGE_KERNEL_ROX);
> + unsigned long section_size;
>
> + section_size = (unsigned long)__start_rodata - (unsigned long)_stext;
> + create_mapping_late(__pa(_stext), (unsigned long)_stext,
> + section_size, PAGE_KERNEL_ROX);
> + /*
> + * mark .rodata as read only. Use _etext rather than __end_rodata to
> + * cover NOTES and EXCEPTION_TABLE.
> + */
> + section_size = (unsigned long)_etext - (unsigned long)__start_rodata;
> + create_mapping_late(__pa(__start_rodata), (unsigned long)__start_rodata,
> + section_size, PAGE_KERNEL_RO);
> }
As you pointed out in the other thread, we'll also need to update
map_kernel to use equivalent chunks for .text and .rodata.
I think we can probably make .rodata RO from the outset in map_kernel,
too.
Could you please update mem_init to log .text and .rodata separately?
It looks like some core code makes assumptions about _etext, so I guess
that has to cover .rodata regardless.
Otherwise, looks good!
Thanks,
Mark.
^ permalink raw reply [flat|nested] 5+ messages in thread* [PATCH] arm64: mm: Mark .rodata as RO
2016-02-12 18:25 ` Mark Rutland
@ 2016-02-16 18:10 ` Kees Cook
2016-02-16 18:48 ` Laura Abbott
0 siblings, 1 reply; 5+ messages in thread
From: Kees Cook @ 2016-02-16 18:10 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, Feb 12, 2016 at 10:25 AM, Mark Rutland <mark.rutland@arm.com> wrote:
> On Fri, Feb 12, 2016 at 10:13:19AM -0600, Jeremy Linton wrote:
>> Currently the .rodata section is actually still executable when DEBUG_RODATA
>> is enabled. This changes that so the .rodata is actually read only, no execute.
>>
>> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Yikes, good catch. Is anyone running the lkdtm tests that check these things?
Reviewed-by: Kees Cook <keescook@chromium.org>
>> ---
>> arch/arm64/kernel/vmlinux.lds.S | 5 +++--
>> arch/arm64/mm/mmu.c | 14 +++++++++++---
>> 2 files changed, 14 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
>> index ab4e436..2e2c053 100644
>> --- a/arch/arm64/kernel/vmlinux.lds.S
>> +++ b/arch/arm64/kernel/vmlinux.lds.S
>> @@ -114,8 +114,9 @@ SECTIONS
>> *(.got) /* Global offset table */
>> }
>>
>> - RO_DATA(PAGE_SIZE)
>> - EXCEPTION_TABLE(8)
>> + ALIGN_DEBUG_RO_MIN(0)
>> + RO_DATA(PAGE_SIZE) /* everything from this point to */
>> + EXCEPTION_TABLE(8) /* _etext will be marked RO NX */
>> NOTES
>>
>> ALIGN_DEBUG_RO_MIN(PAGE_SIZE)
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index ab69a99..a3f4112 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -453,10 +453,18 @@ static void __init map_mem(pgd_t *pgd)
>> #ifdef CONFIG_DEBUG_RODATA
>> void mark_rodata_ro(void)
>> {
>> - create_mapping_late(__pa(_stext), (unsigned long)_stext,
>> - (unsigned long)_etext - (unsigned long)_stext,
>> - PAGE_KERNEL_ROX);
>> + unsigned long section_size;
>>
>> + section_size = (unsigned long)__start_rodata - (unsigned long)_stext;
>> + create_mapping_late(__pa(_stext), (unsigned long)_stext,
>> + section_size, PAGE_KERNEL_ROX);
>> + /*
>> + * mark .rodata as read only. Use _etext rather than __end_rodata to
>> + * cover NOTES and EXCEPTION_TABLE.
>> + */
>> + section_size = (unsigned long)_etext - (unsigned long)__start_rodata;
>> + create_mapping_late(__pa(__start_rodata), (unsigned long)__start_rodata,
>> + section_size, PAGE_KERNEL_RO);
>> }
>
> As you pointed out in the other thread, we'll also need to update
> map_kernel to use equivalent chunks for .text and .rodata.
>
> I think we can probably make .rodata RO from the outset in map_kernel,
> too.
There's a benefit to marking it late in that .rodata can live in the
same (upcoming) section as .data..ro_after_init, which is marked ro
after mark_rodata_ro() to help constify more things.
> Could you please update mem_init to log .text and .rodata separately?
>
> It looks like some core code makes assumptions about _etext, so I guess
> that has to cover .rodata regardless.
>
> Otherwise, looks good!
>
> Thanks,
> Mark.
-Kees
--
Kees Cook
Chrome OS & Brillo Security
^ permalink raw reply [flat|nested] 5+ messages in thread* [PATCH] arm64: mm: Mark .rodata as RO
2016-02-16 18:10 ` Kees Cook
@ 2016-02-16 18:48 ` Laura Abbott
2016-02-16 20:35 ` Kees Cook
0 siblings, 1 reply; 5+ messages in thread
From: Laura Abbott @ 2016-02-16 18:48 UTC (permalink / raw)
To: linux-arm-kernel
On 2/16/16 10:10 AM, Kees Cook wrote:
> On Fri, Feb 12, 2016 at 10:25 AM, Mark Rutland <mark.rutland@arm.com> wrote:
>> On Fri, Feb 12, 2016 at 10:13:19AM -0600, Jeremy Linton wrote:
>>> Currently the .rodata section is actually still executable when DEBUG_RODATA
>>> is enabled. This changes that so the .rodata is actually read only, no execute.
>>>
>>> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
>
> Yikes, good catch. Is anyone running the lkdtm tests that check these things?
>
I don't think the current lkdtm test would have caught this since the exec
test is using rw data and not ro data. That test could be expanded though
to include a rodata buffer as well.
Thanks,
Laura
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] arm64: mm: Mark .rodata as RO
2016-02-16 18:48 ` Laura Abbott
@ 2016-02-16 20:35 ` Kees Cook
0 siblings, 0 replies; 5+ messages in thread
From: Kees Cook @ 2016-02-16 20:35 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Feb 16, 2016 at 10:48 AM, Laura Abbott <laura@labbott.name> wrote:
> On 2/16/16 10:10 AM, Kees Cook wrote:
>>
>> On Fri, Feb 12, 2016 at 10:25 AM, Mark Rutland <mark.rutland@arm.com>
>> wrote:
>>>
>>> On Fri, Feb 12, 2016 at 10:13:19AM -0600, Jeremy Linton wrote:
>>>>
>>>> Currently the .rodata section is actually still executable when
>>>> DEBUG_RODATA
>>>> is enabled. This changes that so the .rodata is actually read only, no
>>>> execute.
>>>>
>>>> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
>>
>>
>> Yikes, good catch. Is anyone running the lkdtm tests that check these
>> things?
>>
>
> I don't think the current lkdtm test would have caught this since the exec
> test is using rw data and not ro data. That test could be expanded though
> to include a rodata buffer as well.
Oh, yeah, excellent point. I'll send a patch.
-Kees
--
Kees Cook
Chrome OS & Brillo Security
^ permalink raw reply [flat|nested] 5+ messages in thread
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2016-02-12 16:13 [PATCH] arm64: mm: Mark .rodata as RO Jeremy Linton
2016-02-12 18:25 ` Mark Rutland
2016-02-16 18:10 ` Kees Cook
2016-02-16 18:48 ` Laura Abbott
2016-02-16 20:35 ` Kees Cook
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