[Buildroot] [PATCH 1/1] qemu: explicitly disable SSP support

[Buildroot] [PATCH 1/1] qemu: explicitly disable SSP support

[Rodrigo Rebello]

Even though the QEMU configure script does a full compile and link test
to detect SSP support, it does so by using the compiler option
-fstack-protector-strong (and then -fstack-protector-all if that fails).

The problem with this method is that the test program passes the check
with -fstack-protector-strong even when SSP support is not available in
the toolchain, since that option restricts stack protection to only a
subset of all the functions in a program and (in the case of the test
program) no "canary" code gets inserted, producing a false-positive.
This causes a subsequent failure when the probe for pthreads is
performed.

To avoid patching the configure script, fix that by simply disabling the
use of stack protector when SSP is known to be unavailable in the
toolchain.

Fixes:

  http://autobuild.buildroot.net/results/efb/efbb4e940543894b8745bb405478a096c90a5ae2/
  http://autobuild.buildroot.net/results/32d/32d6d984febad2dee1f0d31c5fa0aea823297096/
  http://autobuild.buildroot.net/results/aa6/aa6e71c957fb6f07e7bded35a8e47be4dadd042c/
  ...and many others.

Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
---
 package/qemu/qemu.mk | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk
index 94e1bcf..0161b10 100644
--- a/package/qemu/qemu.mk
+++ b/package/qemu/qemu.mk
@@ -133,6 +133,12 @@ QEMU_VARS = \
 	PYTHON=$(HOST_DIR)/usr/bin/python2 \
 	PYTHONPATH=$(TARGET_DIR)/usr/lib/python$(PYTHON_VERSION_MAJOR)/site-packages
 
+# Force disable stack protector when SSP isn't available in toolchain as
+# QEMU configure script fails to properly detect that.
+ifeq ($(BR2_TOOLCHAIN_HAS_SSP),)
+QEMU_OPTS += --disable-stack-protector
+endif
+
 # If we want to specify only a subset of targets, we must still enable all
 # of them, so that QEMU properly builds its list of default targets, from
 # which it then checks if the specified sub-set is valid. That's what we
-- 
2.1.4

[Buildroot] [PATCH 1/1] qemu: explicitly disable SSP support

[Ryan Barnett]

Hi Rodrigo,

On Tue, Nov 10, 2015 at 11:18 AM, Rodrigo Rebello <rprebello@gmail.com> wrote:
> Even though the QEMU configure script does a full compile and link test
> to detect SSP support, it does so by using the compiler option
> -fstack-protector-strong (and then -fstack-protector-all if that fails).
>
> The problem with this method is that the test program passes the check
> with -fstack-protector-strong even when SSP support is not available in
> the toolchain, since that option restricts stack protection to only a
> subset of all the functions in a program and (in the case of the test
> program) no "canary" code gets inserted, producing a false-positive.
> This causes a subsequent failure when the probe for pthreads is
> performed.
>
> To avoid patching the configure script, fix that by simply disabling the
> use of stack protector when SSP is known to be unavailable in the
> toolchain.
>
> Fixes:
>
>   http://autobuild.buildroot.net/results/efb/efbb4e940543894b8745bb405478a096c90a5ae2/
>   http://autobuild.buildroot.net/results/32d/32d6d984febad2dee1f0d31c5fa0aea823297096/
>   http://autobuild.buildroot.net/results/aa6/aa6e71c957fb6f07e7bded35a8e47be4dadd042c/
>   ...and many others.
>
> Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
> ---
>  package/qemu/qemu.mk | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk
> index 94e1bcf..0161b10 100644
> --- a/package/qemu/qemu.mk
> +++ b/package/qemu/qemu.mk
> @@ -133,6 +133,12 @@ QEMU_VARS = \
>         PYTHON=$(HOST_DIR)/usr/bin/python2 \
>         PYTHONPATH=$(TARGET_DIR)/usr/lib/python$(PYTHON_VERSION_MAJOR)/site-packages
>
> +# Force disable stack protector when SSP isn't available in toolchain as
> +# QEMU configure script fails to properly detect that.
> +ifeq ($(BR2_TOOLCHAIN_HAS_SSP),)
> +QEMU_OPTS += --disable-stack-protector
> +endif

Typically when explicitly adding enable/disable configure options both
cases of enabling or disabling the option are put within buildroot. So
for this case, it would become:

# Force disable stack protector when SSP isn't available in toolchain as
# QEMU configure script fails to properly detect that.
ifeq ($(BR2_TOOLCHAIN_HAS_SSP),y)
QEMU_OPTS += --enable-stack-protector
else
QEMU_OPTS += --disable-stack-protector
endif

> +
>  # If we want to specify only a subset of targets, we must still enable all
>  # of them, so that QEMU properly builds its list of default targets, from
>  # which it then checks if the specified sub-set is valid. That's what we

Thanks,
-Ryan

-- 
Ryan Barnett / Sr Software Engineer
Airborne Information Systems / Secure Platforms
MS 131-100, C Ave NE, Cedar Rapids, IA, 52498, USA
ryan.barnett at rockwellcollins.com
www.rockwellcollins.com

[Buildroot] [PATCH 1/1] qemu: explicitly disable SSP support

[Rodrigo Rebello]

Hi, Ryan

2015-11-10 17:49 GMT-02:00 Ryan Barnett <ryan.barnett@rockwellcollins.com>:
> Hi Rodrigo,
>
> On Tue, Nov 10, 2015 at 11:18 AM, Rodrigo Rebello <rprebello@gmail.com> wrote:
>> Even though the QEMU configure script does a full compile and link test
>> to detect SSP support, it does so by using the compiler option
>> -fstack-protector-strong (and then -fstack-protector-all if that fails).
>>
>> The problem with this method is that the test program passes the check
>> with -fstack-protector-strong even when SSP support is not available in
>> the toolchain, since that option restricts stack protection to only a
>> subset of all the functions in a program and (in the case of the test
>> program) no "canary" code gets inserted, producing a false-positive.
>> This causes a subsequent failure when the probe for pthreads is
>> performed.
>>
>> To avoid patching the configure script, fix that by simply disabling the
>> use of stack protector when SSP is known to be unavailable in the
>> toolchain.
>>
>> Fixes:
>>
>>   http://autobuild.buildroot.net/results/efb/efbb4e940543894b8745bb405478a096c90a5ae2/
>>   http://autobuild.buildroot.net/results/32d/32d6d984febad2dee1f0d31c5fa0aea823297096/
>>   http://autobuild.buildroot.net/results/aa6/aa6e71c957fb6f07e7bded35a8e47be4dadd042c/
>>   ...and many others.
>>
>> Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
>> ---
>>  package/qemu/qemu.mk | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk
>> index 94e1bcf..0161b10 100644
>> --- a/package/qemu/qemu.mk
>> +++ b/package/qemu/qemu.mk
>> @@ -133,6 +133,12 @@ QEMU_VARS = \
>>         PYTHON=$(HOST_DIR)/usr/bin/python2 \
>>         PYTHONPATH=$(TARGET_DIR)/usr/lib/python$(PYTHON_VERSION_MAJOR)/site-packages
>>
>> +# Force disable stack protector when SSP isn't available in toolchain as
>> +# QEMU configure script fails to properly detect that.
>> +ifeq ($(BR2_TOOLCHAIN_HAS_SSP),)
>> +QEMU_OPTS += --disable-stack-protector
>> +endif
>
> Typically when explicitly adding enable/disable configure options both
> cases of enabling or disabling the option are put within buildroot. So
> for this case, it would become:
>
> # Force disable stack protector when SSP isn't available in toolchain as
> # QEMU configure script fails to properly detect that.
> ifeq ($(BR2_TOOLCHAIN_HAS_SSP),y)
> QEMU_OPTS += --enable-stack-protector
> else
> QEMU_OPTS += --disable-stack-protector
> endif
>

Ok, then. I'll do as you suggested and send a new patch.

>> +
>>  # If we want to specify only a subset of targets, we must still enable all
>>  # of them, so that QEMU properly builds its list of default targets, from
>>  # which it then checks if the specified sub-set is valid. That's what we
>
> Thanks,
> -Ryan
>
> --
> Ryan Barnett / Sr Software Engineer
> Airborne Information Systems / Secure Platforms
> MS 131-100, C Ave NE, Cedar Rapids, IA, 52498, USA
> ryan.barnett at rockwellcollins.com
> www.rockwellcollins.com

Regards,
Rodrigo

[Buildroot] [PATCH 1/1] qemu: explicitly disable SSP support

[Arnout Vandecappelle]

On 10-11-15 18:18, Rodrigo Rebello wrote:
> Even though the QEMU configure script does a full compile and link test
> to detect SSP support, it does so by using the compiler option
> -fstack-protector-strong (and then -fstack-protector-all if that fails).
> 
> The problem with this method is that the test program passes the check
> with -fstack-protector-strong even when SSP support is not available in
> the toolchain, since that option restricts stack protection to only a
> subset of all the functions in a program and (in the case of the test
> program) no "canary" code gets inserted, producing a false-positive.
> This causes a subsequent failure when the probe for pthreads is
> performed.
> 
> To avoid patching the configure script, fix that by simply disabling the
> use of stack protector when SSP is known to be unavailable in the
> toolchain.

 Actually, it doesn't look too hard to patch the configure script, and that
would be upstreamable.

 But if you feel that that is too difficult, I'm OK with this patch.

 Regards,
 Arnout

> 
> Fixes:
> 
>   http://autobuild.buildroot.net/results/efb/efbb4e940543894b8745bb405478a096c90a5ae2/
>   http://autobuild.buildroot.net/results/32d/32d6d984febad2dee1f0d31c5fa0aea823297096/
>   http://autobuild.buildroot.net/results/aa6/aa6e71c957fb6f07e7bded35a8e47be4dadd042c/
>   ...and many others.
> 
> Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
> ---
>  package/qemu/qemu.mk | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk
> index 94e1bcf..0161b10 100644
> --- a/package/qemu/qemu.mk
> +++ b/package/qemu/qemu.mk
> @@ -133,6 +133,12 @@ QEMU_VARS = \
>  	PYTHON=$(HOST_DIR)/usr/bin/python2 \
>  	PYTHONPATH=$(TARGET_DIR)/usr/lib/python$(PYTHON_VERSION_MAJOR)/site-packages
>  
> +# Force disable stack protector when SSP isn't available in toolchain as
> +# QEMU configure script fails to properly detect that.
> +ifeq ($(BR2_TOOLCHAIN_HAS_SSP),)
> +QEMU_OPTS += --disable-stack-protector
> +endif
> +
>  # If we want to specify only a subset of targets, we must still enable all
>  # of them, so that QEMU properly builds its list of default targets, from
>  # which it then checks if the specified sub-set is valid. That's what we
> 


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [PATCH 1/1] qemu: explicitly disable SSP support

[Rodrigo Rebello]

Arnout, All

2015-11-10 19:11 GMT-02:00 Arnout Vandecappelle <arnout@mind.be>:
> On 10-11-15 18:18, Rodrigo Rebello wrote:
>> Even though the QEMU configure script does a full compile and link test
>> to detect SSP support, it does so by using the compiler option
>> -fstack-protector-strong (and then -fstack-protector-all if that fails).
>>
>> The problem with this method is that the test program passes the check
>> with -fstack-protector-strong even when SSP support is not available in
>> the toolchain, since that option restricts stack protection to only a
>> subset of all the functions in a program and (in the case of the test
>> program) no "canary" code gets inserted, producing a false-positive.
>> This causes a subsequent failure when the probe for pthreads is
>> performed.
>>
>> To avoid patching the configure script, fix that by simply disabling the
>> use of stack protector when SSP is known to be unavailable in the
>> toolchain.
>
>  Actually, it doesn't look too hard to patch the configure script, and that
> would be upstreamable.
>

I agree, that would be a better solution indeed. I'll consider
patching the configure script then, and if I come up with a working
solution, I'll send the patch upstream as well.

>  But if you feel that that is too difficult, I'm OK with this patch.
>
>  Regards,
>  Arnout
>
>>
>> Fixes:
>>
>>   http://autobuild.buildroot.net/results/efb/efbb4e940543894b8745bb405478a096c90a5ae2/
>>   http://autobuild.buildroot.net/results/32d/32d6d984febad2dee1f0d31c5fa0aea823297096/
>>   http://autobuild.buildroot.net/results/aa6/aa6e71c957fb6f07e7bded35a8e47be4dadd042c/
>>   ...and many others.
>>
>> Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
>> ---
>>  package/qemu/qemu.mk | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk
>> index 94e1bcf..0161b10 100644
>> --- a/package/qemu/qemu.mk
>> +++ b/package/qemu/qemu.mk
>> @@ -133,6 +133,12 @@ QEMU_VARS = \
>>       PYTHON=$(HOST_DIR)/usr/bin/python2 \
>>       PYTHONPATH=$(TARGET_DIR)/usr/lib/python$(PYTHON_VERSION_MAJOR)/site-packages
>>
>> +# Force disable stack protector when SSP isn't available in toolchain as
>> +# QEMU configure script fails to properly detect that.
>> +ifeq ($(BR2_TOOLCHAIN_HAS_SSP),)
>> +QEMU_OPTS += --disable-stack-protector
>> +endif
>> +
>>  # If we want to specify only a subset of targets, we must still enable all
>>  # of them, so that QEMU properly builds its list of default targets, from
>>  # which it then checks if the specified sub-set is valid. That's what we
>>
>
>
> --
> Arnout Vandecappelle                          arnout at mind be
> Senior Embedded Software Architect            +32-16-286500
> Essensium/Mind                                http://www.mind.be
> G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
> LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
> GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

Regards,
Rodrigo