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[v9,5/8] powerpc: Set ARCH_HAS_STRICT_MODULE_RWX

Message ID 20210316031741.1004850-5-jniethe5@gmail.com (mailing list archive)
State Changes Requested
Headers show
Series [v9,1/8] powerpc/mm: Implement set_memory() routines | expand
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Context Check Description
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/merge (0512161accb8b6f6dacc85d165350b1812ddcc33)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/next (fbda7904302499dd7ffc073a3c84eb7c9275db0a)
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Commit Message

Jordan Niethe March 16, 2021, 3:17 a.m. UTC 
From: Russell Currey <ruscur@russell.cc>

To enable strict module RWX on powerpc, set:

    CONFIG_STRICT_MODULE_RWX=y

You should also have CONFIG_STRICT_KERNEL_RWX=y set to have any real
security benefit.

ARCH_HAS_STRICT_MODULE_RWX is set to require ARCH_HAS_STRICT_KERNEL_RWX.
This is due to a quirk in arch/Kconfig and arch/powerpc/Kconfig that
makes STRICT_MODULE_RWX *on by default* in configurations where
STRICT_KERNEL_RWX is *unavailable*.

Since this doesn't make much sense, and module RWX without kernel RWX
doesn't make much sense, having the same dependencies as kernel RWX
works around this problem.

Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
---
 arch/powerpc/Kconfig | 1 +
 1 file changed, 1 insertion(+)

Comments

Christophe Leroy March 16, 2021, 6:51 a.m. UTC | #1 
Le 16/03/2021 à 04:17, Jordan Niethe a écrit :
> From: Russell Currey <ruscur@russell.cc>
> 
> To enable strict module RWX on powerpc, set:
> 
>      CONFIG_STRICT_MODULE_RWX=y
> 
> You should also have CONFIG_STRICT_KERNEL_RWX=y set to have any real
> security benefit.
> 
> ARCH_HAS_STRICT_MODULE_RWX is set to require ARCH_HAS_STRICT_KERNEL_RWX.
> This is due to a quirk in arch/Kconfig and arch/powerpc/Kconfig that
> makes STRICT_MODULE_RWX *on by default* in configurations where
> STRICT_KERNEL_RWX is *unavailable*.

Not that easy on book3s/32. On it, you can't protect memory against execution on a page basis, you 
can only do it on a segment basis. So in order to do that, when would need to allocate to areas of 
memory: one in module space for text and one in vmalloc space for data.

See https://github.com/linuxppc/linux/commit/6ca05532 and 
https://github.com/linuxppc/linux/commit/7fbc22ce


> 
> Since this doesn't make much sense, and module RWX without kernel RWX
> doesn't make much sense, having the same dependencies as kernel RWX
> works around this problem.
> 
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> ---
>   arch/powerpc/Kconfig | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 4498a27ac9db..d9cadc4212d0 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -137,6 +137,7 @@ config PPC
>   	select ARCH_HAS_SCALED_CPUTIME		if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
>   	select ARCH_HAS_SET_MEMORY
>   	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !HIBERNATION)
> +	select ARCH_HAS_STRICT_MODULE_RWX	if ARCH_HAS_STRICT_KERNEL_RWX
>   	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
>   	select ARCH_HAS_UACCESS_FLUSHCACHE
>   	select ARCH_HAS_COPY_MC			if PPC64
>
Jordan Niethe March 17, 2021, 2:15 a.m. UTC | #2 
On Tue, Mar 16, 2021 at 5:51 PM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 16/03/2021 à 04:17, Jordan Niethe a écrit :
> > From: Russell Currey <ruscur@russell.cc>
> >
> > To enable strict module RWX on powerpc, set:
> >
> >      CONFIG_STRICT_MODULE_RWX=y
> >
> > You should also have CONFIG_STRICT_KERNEL_RWX=y set to have any real
> > security benefit.
> >
> > ARCH_HAS_STRICT_MODULE_RWX is set to require ARCH_HAS_STRICT_KERNEL_RWX.
> > This is due to a quirk in arch/Kconfig and arch/powerpc/Kconfig that
> > makes STRICT_MODULE_RWX *on by default* in configurations where
> > STRICT_KERNEL_RWX is *unavailable*.
>
> Not that easy on book3s/32. On it, you can't protect memory against execution on a page basis, you
> can only do it on a segment basis. So in order to do that, when would need to allocate to areas of
> memory: one in module space for text and one in vmalloc space for data.
>
> See https://github.com/linuxppc/linux/commit/6ca05532 and
> https://github.com/linuxppc/linux/commit/7fbc22ce
Would it be ok to just make ARCH_HAS_STRICT_MODULE_RWX conditional on 64s?
>
>
> >
> > Since this doesn't make much sense, and module RWX without kernel RWX
> > doesn't make much sense, having the same dependencies as kernel RWX
> > works around this problem.
> >
> > Signed-off-by: Russell Currey <ruscur@russell.cc>
> > Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> > ---
> >   arch/powerpc/Kconfig | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > index 4498a27ac9db..d9cadc4212d0 100644
> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -137,6 +137,7 @@ config PPC
> >       select ARCH_HAS_SCALED_CPUTIME          if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
> >       select ARCH_HAS_SET_MEMORY
> >       select ARCH_HAS_STRICT_KERNEL_RWX       if ((PPC_BOOK3S_64 || PPC32) && !HIBERNATION)
> > +     select ARCH_HAS_STRICT_MODULE_RWX       if ARCH_HAS_STRICT_KERNEL_RWX
> >       select ARCH_HAS_TICK_BROADCAST          if GENERIC_CLOCKEVENTS_BROADCAST
> >       select ARCH_HAS_UACCESS_FLUSHCACHE
> >       select ARCH_HAS_COPY_MC                 if PPC64
> >
Christophe Leroy March 17, 2021, 5:43 a.m. UTC | #3 
Le 17/03/2021 à 03:15, Jordan Niethe a écrit :
> On Tue, Mar 16, 2021 at 5:51 PM Christophe Leroy
> <christophe.leroy@csgroup.eu> wrote:
>>
>>
>>
>> Le 16/03/2021 à 04:17, Jordan Niethe a écrit :
>>> From: Russell Currey <ruscur@russell.cc>
>>>
>>> To enable strict module RWX on powerpc, set:
>>>
>>>       CONFIG_STRICT_MODULE_RWX=y
>>>
>>> You should also have CONFIG_STRICT_KERNEL_RWX=y set to have any real
>>> security benefit.
>>>
>>> ARCH_HAS_STRICT_MODULE_RWX is set to require ARCH_HAS_STRICT_KERNEL_RWX.
>>> This is due to a quirk in arch/Kconfig and arch/powerpc/Kconfig that
>>> makes STRICT_MODULE_RWX *on by default* in configurations where
>>> STRICT_KERNEL_RWX is *unavailable*.
>>
>> Not that easy on book3s/32. On it, you can't protect memory against execution on a page basis, you
>> can only do it on a segment basis. So in order to do that, when would need to allocate to areas of
>> memory: one in module space for text and one in vmalloc space for data.
>>
>> See https://github.com/linuxppc/linux/commit/6ca05532 and
>> https://github.com/linuxppc/linux/commit/7fbc22ce
> Would it be ok to just make ARCH_HAS_STRICT_MODULE_RWX conditional on 64s?

I think making it conditional on !PPC_BOOK3S_604 should be enough.

>>
>>
>>>
>>> Since this doesn't make much sense, and module RWX without kernel RWX
>>> doesn't make much sense, having the same dependencies as kernel RWX
>>> works around this problem.
>>>
>>> Signed-off-by: Russell Currey <ruscur@russell.cc>
>>> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
>>> ---
>>>    arch/powerpc/Kconfig | 1 +
>>>    1 file changed, 1 insertion(+)
>>>
>>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>>> index 4498a27ac9db..d9cadc4212d0 100644
>>> --- a/arch/powerpc/Kconfig
>>> +++ b/arch/powerpc/Kconfig
>>> @@ -137,6 +137,7 @@ config PPC
>>>        select ARCH_HAS_SCALED_CPUTIME          if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
>>>        select ARCH_HAS_SET_MEMORY
>>>        select ARCH_HAS_STRICT_KERNEL_RWX       if ((PPC_BOOK3S_64 || PPC32) && !HIBERNATION)
>>> +     select ARCH_HAS_STRICT_MODULE_RWX       if ARCH_HAS_STRICT_KERNEL_RWX
>>>        select ARCH_HAS_TICK_BROADCAST          if GENERIC_CLOCKEVENTS_BROADCAST
>>>        select ARCH_HAS_UACCESS_FLUSHCACHE
>>>        select ARCH_HAS_COPY_MC                 if PPC64
>>>
diff mbox series

Patch

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 4498a27ac9db..d9cadc4212d0 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -137,6 +137,7 @@  config PPC
 	select ARCH_HAS_SCALED_CPUTIME		if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
 	select ARCH_HAS_SET_MEMORY
 	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !HIBERNATION)
+	select ARCH_HAS_STRICT_MODULE_RWX	if ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UACCESS_FLUSHCACHE
 	select ARCH_HAS_COPY_MC			if PPC64