qemu: explicitly disable SSP support

PATCH New Rodrigo Rebello 3 participants 5 messages Nov 10, 2015

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Rodrigo Rebello

author

2015-11-10 17:18 UTC #0 lore raw

PATCH 1/1 qemu: explicitly disable SSP support

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 <[email protected]>

---
 package/qemu/qemu.mk | 6 ++++++
 1 file changed, 6 insertions(+)

package/qemu/qemu.mk +6 -0

index 94e1bcf..0161b10 100644
@@ -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

Signature · 1 line

2.1.4

Ryan Barnett

2015-11-10 19:49 UTC #1 lore raw

PATCH 1/1 qemu: explicitly disable SSP support

Hi Rodrigo,

Quoted 33 lines · 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 <[email protected]>
---
 package/qemu/qemu.mk | 6 ++++++
 1 file changed, 6 insertions(+)
package/qemu/qemu.mk +0 -0
index 94e1bcf..0161b10 100644

package/qemu/qemu.mk QEMU_VARS = \ · line 140

Quoted 8 lines

package/qemu/qemu.mk +5 -0

@@ -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

package/qemu/qemu.mk QEMU_VARS = \ · line 144

Quoted 4 lines

package/qemu/qemu.mk +1 -0

+
 # 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

Signature · 5 lines

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

Rodrigo Rebello

author

2015-11-10 20:47 UTC #2 lore raw

PATCH 1/1 qemu: explicitly disable SSP support

Hi, Ryan

2015-11-10 17:49 GMT-02:00 Ryan Barnett <[email protected]>:

Quoted 49 lines

Hi Rodrigo,
Quoted 33 lines · 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 <[email protected]>
---
 package/qemu/qemu.mk | 6 ++++++
 1 file changed, 6 insertions(+)
package/qemu/qemu.mk +0 -0
index 94e1bcf..0161b10 100644
package/qemu/qemu.mk QEMU_VARS = \ · line 140
Quoted 8 lines
package/qemu/qemu.mk +5 -0
@@ -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:

Quoted 8 lines

# 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.

Quoted 8 lines

package/qemu/qemu.mk QEMU_VARS = \ · line 144

Quoted 4 lines

package/qemu/qemu.mk +1 -0

+
 # 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

Quoted 6 lines

--
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

Arnout Vandecappelle

2015-11-10 21:11 UTC #3 lore raw

PATCH 1/1 qemu: explicitly disable SSP support

In reply to Rodrigo Rebello

Quoted 12 lines · 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.

Quoted 3 lines

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

Quoted 31 lines

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 <[email protected]>
---
 package/qemu/qemu.mk | 6 ++++++
 1 file changed, 6 insertions(+)
package/qemu/qemu.mk +6 -0
index 94e1bcf..0161b10 100644
@@ -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

Signature · 6 lines

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

Rodrigo Rebello

author

2015-11-10 21:22 UTC #4 lore raw

PATCH 1/1 qemu: explicitly disable SSP support

Arnout, All

2015-11-10 19:11 GMT-02:00 Arnout Vandecappelle <[email protected]>:

Quoted 13 lines · Rodrigo Rebello

Quoted 12 lines
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.

Quoted 7 lines

Quoted 3 lines
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.

Quoted 39 lines

But if you feel that that is too difficult, I'm OK with this patch.
Regards,
Arnout
Quoted 21 lines
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 <[email protected]>
---
 package/qemu/qemu.mk | 6 ++++++
 1 file changed, 6 insertions(+)
package/qemu/qemu.mk +0 -0
index 94e1bcf..0161b10 100644
@@ -133,6 +133,12 @@ QEMU_VARS = \
      PYTHON=$(HOST_DIR)/usr/bin/python2 \
      PYTHONPATH=$(TARGET_DIR)/usr/lib/python$(PYTHON_VERSION_MAJOR)/site-packages
package/qemu/qemu.mk QEMU_VARS = \ · line 144
Quoted 10 lines
package/qemu/qemu.mk +6 -0
 
+# 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
--

Quoted 6 lines

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