[PATCHv2 0/2] Hardening configs refactor/rename

[PATCHv2 0/2] Hardening configs refactor/rename

[Laura Abbott]

Hi,

This is a follow up to my proposal to rename/refactor CONFIG_DEBUG_RODATA
and CONFIG_DEBUG_SET_MODULE_RONX. Among other objections, there shouldn't
be 'debug' in the name since these provide necessary kernel protection.

v2 takes a slightly different approach to this per feedback. Patch #1 moves
CONFIG_DEBUG_RODATA and CONFIG_DEBUG_SET_MODULE_RONX to a common arch config.
These configs are def_bool y for every arch except !CPU_V7 for arm
CONFIG_DEBUG_RODATA. I think this also mitigates another concern about changing
the name since these are basically internal configs at this point and not end
user selectable. Patch #2 does the rename to something more descriptive.
Hopefully this should separate discussion more clearly into two parts (refactor
and rename)

Thanks,
Laura


Laura Abbott (2):
  arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common
  arch: Rename CONFIG_DEBUG_RODATA and CONFIG_DEBUG_MODULE_RONX

 Documentation/DocBook/kgdb.tmpl            |  8 ++++----
 Documentation/security/self-protection.txt |  4 ++--
 arch/Kconfig                               | 28 ++++++++++++++++++++++++++++
 arch/arm/Kconfig                           |  3 +++
 arch/arm/Kconfig.debug                     | 11 -----------
 arch/arm/configs/aspeed_g4_defconfig       |  3 +--
 arch/arm/configs/aspeed_g5_defconfig       |  3 +--
 arch/arm/include/asm/cacheflush.h          |  2 +-
 arch/arm/kernel/patch.c                    |  4 ++--
 arch/arm/kernel/vmlinux.lds.S              |  8 ++++----
 arch/arm/mm/Kconfig                        | 14 +-------------
 arch/arm/mm/init.c                         |  4 ++--
 arch/arm64/Kconfig                         |  5 ++---
 arch/arm64/Kconfig.debug                   | 13 +------------
 arch/arm64/kernel/insn.c                   |  2 +-
 arch/parisc/Kconfig                        |  1 +
 arch/parisc/Kconfig.debug                  | 11 -----------
 arch/parisc/configs/712_defconfig          |  1 -
 arch/parisc/configs/c3000_defconfig        |  1 -
 arch/parisc/mm/init.c                      |  2 +-
 arch/s390/Kconfig                          |  5 ++---
 arch/s390/Kconfig.debug                    |  3 ---
 arch/x86/Kconfig                           |  5 ++---
 arch/x86/Kconfig.debug                     | 11 -----------
 include/linux/filter.h                     |  4 ++--
 include/linux/init.h                       |  4 ++--
 include/linux/module.h                     |  2 +-
 init/main.c                                |  4 ++--
 kernel/configs/android-recommended.config  |  2 +-
 kernel/module.c                            |  6 +++---
 kernel/power/hibernate.c                   |  2 +-
 kernel/power/power.h                       |  4 ++--
 kernel/power/snapshot.c                    |  4 ++--
 33 files changed, 75 insertions(+), 109 deletions(-)

-- 
2.7.4

[PATCHv2 1/2] arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common

[Laura Abbott]

There are multiple architectures that support CONFIG_DEBUG_RODATA and
CONFIG_SET_MODULE_RONX. These options also now have the ability to be
turned off at runtime. Move these to an architecture independent
location and make these options def_bool y for almost all of those
arches.

Signed-off-by: Laura Abbott <labbott@redhat.com>
---
v2: This patch is now doing just the refactor of the existing config options.
---
 arch/Kconfig              | 28 ++++++++++++++++++++++++++++
 arch/arm/Kconfig          |  3 +++
 arch/arm/Kconfig.debug    | 11 -----------
 arch/arm/mm/Kconfig       | 12 ------------
 arch/arm64/Kconfig        |  5 ++---
 arch/arm64/Kconfig.debug  | 11 -----------
 arch/parisc/Kconfig       |  1 +
 arch/parisc/Kconfig.debug | 11 -----------
 arch/s390/Kconfig         |  5 ++---
 arch/s390/Kconfig.debug   |  3 ---
 arch/x86/Kconfig          |  5 ++---
 arch/x86/Kconfig.debug    | 11 -----------
 12 files changed, 38 insertions(+), 68 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 99839c2..22ee01e 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -781,4 +781,32 @@ config VMAP_STACK
 	  the stack to map directly to the KASAN shadow map using a formula
 	  that is incorrect if the stack is in vmalloc space.
 
+config ARCH_NO_STRICT_RWX_DEFAULTS
+	def_bool n
+
+config ARCH_HAS_STRICT_KERNEL_RWX
+	def_bool n
+
+config DEBUG_RODATA
+	def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
+	prompt "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
+	depends on ARCH_HAS_STRICT_KERNEL_RWX
+	help
+	  If this is set, kernel text and rodata memory will be made read-only,
+	  and non-text memory will be made non-executable. This provides
+	  protection against certain security exploits (e.g. executing the heap
+	  or modifying text)
+
+config ARCH_HAS_STRICT_MODULE_RWX
+	def_bool n
+
+config DEBUG_SET_MODULE_RONX
+	def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
+	prompt "Set loadable kenrel module data as NX and text as RO" if ARCH_NO_STRICT_RWX_DEFAULTS
+	depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
+	help
+	  If this is set, module text and rodata memory will be made read-only,
+	  and non-text memory will be made non-executable. This provides
+	  protection against certain security exploits (e.g. writing to text)
+
 source "kernel/gcov/Kconfig"
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 186c4c2..aa73ca8 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -4,10 +4,13 @@ config ARM
 	select ARCH_CLOCKSOURCE_DATA
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ELF_RANDOMIZE
+	select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
+	select ARCH_HAS_STRICT_MODULE_RWX if MMU
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAVE_CUSTOM_GPIO_H
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_MIGHT_HAVE_PC_PARPORT
+	select ARCH_NO_STRICT_RWX_DEFAULTS if !CPU_V7
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF
diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index d83f7c3..426d271 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -1738,17 +1738,6 @@ config PID_IN_CONTEXTIDR
 	  additional instructions during context switch. Say Y here only if you
 	  are planning to use hardware trace tools with this kernel.
 
-config DEBUG_SET_MODULE_RONX
-	bool "Set loadable kernel module data as NX and text as RO"
-	depends on MODULES && MMU
-	---help---
-	  This option helps catch unintended modifications to loadable
-	  kernel module's text and read-only data. It also prevents execution
-	  of module data. Such protection may interfere with run-time code
-	  patching and dynamic kernel tracing - and they might also protect
-	  against certain classes of kernel exploits.
-	  If in doubt, say "N".
-
 source "drivers/hwtracing/coresight/Kconfig"
 
 endmenu
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index f68e8ec..419a035 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -1051,18 +1051,6 @@ config ARCH_SUPPORTS_BIG_ENDIAN
 	  This option specifies the architecture can support big endian
 	  operation.
 
-config DEBUG_RODATA
-	bool "Make kernel text and rodata read-only"
-	depends on MMU && !XIP_KERNEL
-	default y if CPU_V7
-	help
-	  If this is set, kernel text and rodata memory will be made
-	  read-only, and non-text kernel memory will be made non-executable.
-	  The tradeoff is that each region is padded to section-size (1MiB)
-	  boundaries (because their permissions are different and splitting
-	  the 1M pages into 4K ones causes TLB performance problems), which
-	  can waste memory.
-
 config DEBUG_ALIGN_RODATA
 	bool "Make rodata strictly non-executable"
 	depends on DEBUG_RODATA
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1117421..e1efbcc 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -13,6 +13,8 @@ config ARM64
 	select ARCH_HAS_GIGANTIC_PAGE
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_SG_CHAIN
+	select ARCH_HAS_STRICT_KERNEL_RWX
+	select ARCH_HAS_STRICT_MODULE_RWX
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select ARCH_SUPPORTS_ATOMIC_RMW
@@ -123,9 +125,6 @@ config ARCH_PHYS_ADDR_T_64BIT
 config MMU
 	def_bool y
 
-config DEBUG_RODATA
-	def_bool y
-
 config ARM64_PAGE_SHIFT
 	int
 	default 16 if ARM64_64K_PAGES
diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index d1ebd46..939815e 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -71,17 +71,6 @@ config DEBUG_WX
 
 	  If in doubt, say "Y".
 
-config DEBUG_SET_MODULE_RONX
-	bool "Set loadable kernel module data as NX and text as RO"
-	depends on MODULES
-	default y
-	help
-	  Is this is set, kernel module text and rodata will be made read-only.
-	  This is to help catch accidental or malicious attempts to change the
-	  kernel's executable code.
-
-	  If in doubt, say Y.
-
 config DEBUG_ALIGN_RODATA
 	depends on DEBUG_RODATA
 	bool "Align linker sections up to SECTION_SIZE"
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 3a71f38..ad294b3 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -8,6 +8,7 @@ config PARISC
 	select HAVE_SYSCALL_TRACEPOINTS
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_HAS_ELF_RANDOMIZE
+	select ARCH_HAS_STRICT_KERNEL_RWX
 	select RTC_CLASS
 	select RTC_DRV_GENERIC
 	select INIT_ALL_POSSIBLE
diff --git a/arch/parisc/Kconfig.debug b/arch/parisc/Kconfig.debug
index 68b7cbd..0d856b9 100644
--- a/arch/parisc/Kconfig.debug
+++ b/arch/parisc/Kconfig.debug
@@ -5,15 +5,4 @@ source "lib/Kconfig.debug"
 config TRACE_IRQFLAGS_SUPPORT
 	def_bool y
 
-config DEBUG_RODATA
-       bool "Write protect kernel read-only data structures"
-       depends on DEBUG_KERNEL
-       default y
-       help
-         Mark the kernel read-only data as write-protected in the pagetables,
-         in order to catch accidental (and incorrect) writes to such const
-         data. This option may have a slight performance impact because a
-         portion of the kernel code won't be covered by a TLB anymore.
-         If in doubt, say "N".
-
 endmenu
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index c6722112..53bb0e3 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -62,9 +62,6 @@ config PCI_QUIRKS
 config ARCH_SUPPORTS_UPROBES
 	def_bool y
 
-config DEBUG_RODATA
-	def_bool y
-
 config S390
 	def_bool y
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
@@ -73,6 +70,8 @@ config S390
 	select ARCH_HAS_GIGANTIC_PAGE
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_SG_CHAIN
+	select ARCH_HAS_STRICT_KERNEL_RWX
+	select ARCH_HAS_STRICT_MODULE_RWX
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select ARCH_INLINE_READ_LOCK
diff --git a/arch/s390/Kconfig.debug b/arch/s390/Kconfig.debug
index 26c5d5be..57f8ea9 100644
--- a/arch/s390/Kconfig.debug
+++ b/arch/s390/Kconfig.debug
@@ -17,7 +17,4 @@ config S390_PTDUMP
 	  kernel.
 	  If in doubt, say "N"
 
-config DEBUG_SET_MODULE_RONX
-	def_bool y
-	depends on MODULES
 endmenu
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e487493..13e1bf4 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -54,6 +54,8 @@ config X86
 	select ARCH_HAS_MMIO_FLUSH
 	select ARCH_HAS_PMEM_API		if X86_64
 	select ARCH_HAS_SG_CHAIN
+	select ARCH_HAS_STRICT_KERNEL_RWX
+	select ARCH_HAS_STRICT_MODULE_RWX
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select ARCH_MIGHT_HAVE_ACPI_PDC		if ACPI
@@ -309,9 +311,6 @@ config ARCH_SUPPORTS_UPROBES
 config FIX_EARLYCON_MEM
 	def_bool y
 
-config DEBUG_RODATA
-	def_bool y
-
 config PGTABLE_LEVELS
 	int
 	default 4 if X86_64
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 67eec55..69cdd0b 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -109,17 +109,6 @@ config DEBUG_WX
 
 	  If in doubt, say "Y".
 
-config DEBUG_SET_MODULE_RONX
-	bool "Set loadable kernel module data as NX and text as RO"
-	depends on MODULES
-	---help---
-	  This option helps catch unintended modifications to loadable
-	  kernel module's text and read-only data. It also prevents execution
-	  of module data. Such protection may interfere with run-time code
-	  patching and dynamic kernel tracing - and they might also protect
-	  against certain classes of kernel exploits.
-	  If in doubt, say "N".
-
 config DEBUG_NX_TEST
 	tristate "Testcase for the NX non-executable stack feature"
 	depends on DEBUG_KERNEL && m
-- 
2.7.4

[PATCHv2 2/2] arch: Rename CONFIG_DEBUG_RODATA and CONFIG_DEBUG_MODULE_RONX

[Laura Abbott]

Both of these options are poorly named. The features they provide are
necessary for system security and should not be considered debug only.
Change the name to something that accurately describes what these
options do.

Signed-off-by: Laura Abbott <labbott@redhat.com>
---
v2: This patch is now doing the renaming of CONFIG_DEBUG_RODATA and
CONFIG_DEBUG_MODULE_RONX
---
 Documentation/DocBook/kgdb.tmpl            | 8 ++++----
 Documentation/security/self-protection.txt | 4 ++--
 arch/Kconfig                               | 4 ++--
 arch/arm/configs/aspeed_g4_defconfig       | 3 +--
 arch/arm/configs/aspeed_g5_defconfig       | 3 +--
 arch/arm/include/asm/cacheflush.h          | 2 +-
 arch/arm/kernel/patch.c                    | 4 ++--
 arch/arm/kernel/vmlinux.lds.S              | 8 ++++----
 arch/arm/mm/Kconfig                        | 2 +-
 arch/arm/mm/init.c                         | 4 ++--
 arch/arm64/Kconfig.debug                   | 2 +-
 arch/arm64/kernel/insn.c                   | 2 +-
 arch/parisc/configs/712_defconfig          | 1 -
 arch/parisc/configs/c3000_defconfig        | 1 -
 arch/parisc/mm/init.c                      | 2 +-
 include/linux/filter.h                     | 4 ++--
 include/linux/init.h                       | 4 ++--
 include/linux/module.h                     | 2 +-
 init/main.c                                | 4 ++--
 kernel/configs/android-recommended.config  | 2 +-
 kernel/module.c                            | 6 +++---
 kernel/power/hibernate.c                   | 2 +-
 kernel/power/power.h                       | 4 ++--
 kernel/power/snapshot.c                    | 4 ++--
 24 files changed, 39 insertions(+), 43 deletions(-)

diff --git a/Documentation/DocBook/kgdb.tmpl b/Documentation/DocBook/kgdb.tmpl
index f3abca7..856ac20 100644
--- a/Documentation/DocBook/kgdb.tmpl
+++ b/Documentation/DocBook/kgdb.tmpl
@@ -115,12 +115,12 @@
     </para>
     <para>
     If the architecture that you are using supports the kernel option
-    CONFIG_DEBUG_RODATA, you should consider turning it off.  This
+    CONFIG_STRICT_KERNEL_RWX, you should consider turning it off.  This
     option will prevent the use of software breakpoints because it
     marks certain regions of the kernel's memory space as read-only.
     If kgdb supports it for the architecture you are using, you can
     use hardware breakpoints if you desire to run with the
-    CONFIG_DEBUG_RODATA option turned on, else you need to turn off
+    CONFIG_STRICT_KERNEL_RWX option turned on, else you need to turn off
     this option.
     </para>
     <para>
@@ -135,7 +135,7 @@
     <para>Here is an example set of .config symbols to enable or
     disable for kgdb:
     <itemizedlist>
-    <listitem><para># CONFIG_DEBUG_RODATA is not set</para></listitem>
+    <listitem><para># CONFIG_STRICT_KERNEL_RWX is not set</para></listitem>
     <listitem><para>CONFIG_FRAME_POINTER=y</para></listitem>
     <listitem><para>CONFIG_KGDB=y</para></listitem>
     <listitem><para>CONFIG_KGDB_SERIAL_CONSOLE=y</para></listitem>
@@ -166,7 +166,7 @@
     </para>
     <para>Here is an example set of .config symbols to enable/disable kdb:
     <itemizedlist>
-    <listitem><para># CONFIG_DEBUG_RODATA is not set</para></listitem>
+    <listitem><para># CONFIG_STRICT_KERNEL_RWX is not set</para></listitem>
     <listitem><para>CONFIG_FRAME_POINTER=y</para></listitem>
     <listitem><para>CONFIG_KGDB=y</para></listitem>
     <listitem><para>CONFIG_KGDB_SERIAL_CONSOLE=y</para></listitem>
diff --git a/Documentation/security/self-protection.txt b/Documentation/security/self-protection.txt
index 3010576..dd2a3b1 100644
--- a/Documentation/security/self-protection.txt
+++ b/Documentation/security/self-protection.txt
@@ -51,8 +51,8 @@ kernel, they are implemented in a way where the memory is temporarily
 made writable during the update, and then returned to the original
 permissions.)
 
-In support of this are (the poorly named) CONFIG_DEBUG_RODATA and
-CONFIG_DEBUG_SET_MODULE_RONX, which seek to make sure that code is not
+In support of this are CONFIG_STRICT_KERNEL_RWX and
+CONFIG_STRICT_MODULE_RWX, which seek to make sure that code is not
 writable, data is not executable, and read-only data is neither writable
 nor executable.
 
diff --git a/arch/Kconfig b/arch/Kconfig
index 22ee01e..406f6cd 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -787,7 +787,7 @@ config ARCH_NO_STRICT_RWX_DEFAULTS
 config ARCH_HAS_STRICT_KERNEL_RWX
 	def_bool n
 
-config DEBUG_RODATA
+config STRICT_KERNEL_RWX
 	def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
 	prompt "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
 	depends on ARCH_HAS_STRICT_KERNEL_RWX
@@ -800,7 +800,7 @@ config DEBUG_RODATA
 config ARCH_HAS_STRICT_MODULE_RWX
 	def_bool n
 
-config DEBUG_SET_MODULE_RONX
+config STRICT_MODULE_RWX
 	def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
 	prompt "Set loadable kenrel module data as NX and text as RO" if ARCH_NO_STRICT_RWX_DEFAULTS
 	depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
diff --git a/arch/arm/configs/aspeed_g4_defconfig b/arch/arm/configs/aspeed_g4_defconfig
index ca39c04..beea2cc 100644
--- a/arch/arm/configs/aspeed_g4_defconfig
+++ b/arch/arm/configs/aspeed_g4_defconfig
@@ -25,7 +25,6 @@ CONFIG_MODULE_UNLOAD=y
 # CONFIG_ARCH_MULTI_V7 is not set
 CONFIG_ARCH_ASPEED=y
 CONFIG_MACH_ASPEED_G4=y
-CONFIG_DEBUG_RODATA=y
 CONFIG_AEABI=y
 CONFIG_UACCESS_WITH_MEMCPY=y
 CONFIG_SECCOMP=y
@@ -79,7 +78,7 @@ CONFIG_DEBUG_LL_UART_8250=y
 CONFIG_DEBUG_UART_PHYS=0x1e784000
 CONFIG_DEBUG_UART_VIRT=0xe8784000
 CONFIG_EARLY_PRINTK=y
-CONFIG_DEBUG_SET_MODULE_RONX=y
+CONFIG_STRICT_MODULE_RWX=y
 # CONFIG_XZ_DEC_X86 is not set
 # CONFIG_XZ_DEC_POWERPC is not set
 # CONFIG_XZ_DEC_IA64 is not set
diff --git a/arch/arm/configs/aspeed_g5_defconfig b/arch/arm/configs/aspeed_g5_defconfig
index 4f366b0..0e245e5 100644
--- a/arch/arm/configs/aspeed_g5_defconfig
+++ b/arch/arm/configs/aspeed_g5_defconfig
@@ -26,7 +26,6 @@ CONFIG_ARCH_MULTI_V6=y
 # CONFIG_ARCH_MULTI_V7 is not set
 CONFIG_ARCH_ASPEED=y
 CONFIG_MACH_ASPEED_G5=y
-CONFIG_DEBUG_RODATA=y
 CONFIG_AEABI=y
 CONFIG_UACCESS_WITH_MEMCPY=y
 CONFIG_SECCOMP=y
@@ -81,7 +80,7 @@ CONFIG_DEBUG_LL_UART_8250=y
 CONFIG_DEBUG_UART_PHYS=0x1e784000
 CONFIG_DEBUG_UART_VIRT=0xe8784000
 CONFIG_EARLY_PRINTK=y
-CONFIG_DEBUG_SET_MODULE_RONX=y
+CONFIG_STRICT_MODULE_RWX=y
 # CONFIG_XZ_DEC_X86 is not set
 # CONFIG_XZ_DEC_POWERPC is not set
 # CONFIG_XZ_DEC_IA64 is not set
diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index bdd283b..02454fa 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -490,7 +490,7 @@ static inline int set_memory_x(unsigned long addr, int numpages) { return 0; }
 static inline int set_memory_nx(unsigned long addr, int numpages) { return 0; }
 #endif
 
-#ifdef CONFIG_DEBUG_RODATA
+#ifdef CONFIG_STRICT_KERNEL_RWX
 void set_kernel_text_rw(void);
 void set_kernel_text_ro(void);
 #else
diff --git a/arch/arm/kernel/patch.c b/arch/arm/kernel/patch.c
index 69bda1a..020560b 100644
--- a/arch/arm/kernel/patch.c
+++ b/arch/arm/kernel/patch.c
@@ -24,9 +24,9 @@ static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
 	bool module = !core_kernel_text(uintaddr);
 	struct page *page;
 
-	if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
+	if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
 		page = vmalloc_to_page(addr);
-	else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA))
+	else if (!module && IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
 		page = virt_to_page(addr);
 	else
 		return addr;
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index f7f55df..ce18007 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -97,7 +97,7 @@ SECTIONS
 		HEAD_TEXT
 	}
 
-#ifdef CONFIG_DEBUG_RODATA
+#ifdef CONFIG_STRICT_KERNEL_RWX
 	. = ALIGN(1<<SECTION_SHIFT);
 #endif
 
@@ -158,7 +158,7 @@ SECTIONS
 
 	NOTES
 
-#ifdef CONFIG_DEBUG_RODATA
+#ifdef CONFIG_STRICT_KERNEL_RWX
 	. = ALIGN(1<<SECTION_SHIFT);
 #else
 	. = ALIGN(PAGE_SIZE);
@@ -230,7 +230,7 @@ SECTIONS
 	PERCPU_SECTION(L1_CACHE_BYTES)
 #endif
 
-#ifdef CONFIG_DEBUG_RODATA
+#ifdef CONFIG_STRICT_KERNEL_RWX
 	. = ALIGN(1<<SECTION_SHIFT);
 #else
 	. = ALIGN(THREAD_SIZE);
@@ -325,7 +325,7 @@ SECTIONS
 	STABS_DEBUG
 }
 
-#ifdef CONFIG_DEBUG_RODATA
+#ifdef CONFIG_STRICT_KERNEL_RWX
 /*
  * Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
  * be the first section-aligned location after __start_rodata. Otherwise,
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 419a035..35e3a56 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -1053,7 +1053,7 @@ config ARCH_SUPPORTS_BIG_ENDIAN
 
 config DEBUG_ALIGN_RODATA
 	bool "Make rodata strictly non-executable"
-	depends on DEBUG_RODATA
+	depends on STRICT_KERNEL_RWX
 	default y
 	help
 	  If this is set, rodata will be made explicitly non-executable. This
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 370581a..4be0bee 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -572,7 +572,7 @@ void __init mem_init(void)
 	}
 }
 
-#ifdef CONFIG_DEBUG_RODATA
+#ifdef CONFIG_STRICT_KERNEL_RWX
 struct section_perm {
 	const char *name;
 	unsigned long start;
@@ -741,7 +741,7 @@ void set_kernel_text_ro(void)
 
 #else
 static inline void fix_kernmem_perms(void) { }
-#endif /* CONFIG_DEBUG_RODATA */
+#endif /* CONFIG_STRICT_KERNEL_RWX */
 
 void free_tcmmem(void)
 {
diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index 939815e..560a8d8 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -72,7 +72,7 @@ config DEBUG_WX
 	  If in doubt, say "Y".
 
 config DEBUG_ALIGN_RODATA
-	depends on DEBUG_RODATA
+	depends on STRICT_KERNEL_RWX
 	bool "Align linker sections up to SECTION_SIZE"
 	help
 	  If this option is enabled, sections that may potentially be marked as
diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index 94b62c1..67f9cb9 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -93,7 +93,7 @@ static void __kprobes *patch_map(void *addr, int fixmap)
 	bool module = !core_kernel_text(uintaddr);
 	struct page *page;
 
-	if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
+	if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
 		page = vmalloc_to_page(addr);
 	else if (!module)
 		page = pfn_to_page(PHYS_PFN(__pa(addr)));
diff --git a/arch/parisc/configs/712_defconfig b/arch/parisc/configs/712_defconfig
index db8f56b..143d026 100644
--- a/arch/parisc/configs/712_defconfig
+++ b/arch/parisc/configs/712_defconfig
@@ -182,7 +182,6 @@ CONFIG_DEBUG_FS=y
 CONFIG_DEBUG_KERNEL=y
 CONFIG_DEBUG_MUTEXES=y
 # CONFIG_RCU_CPU_STALL_DETECTOR is not set
-CONFIG_DEBUG_RODATA=y
 CONFIG_CRYPTO_NULL=m
 CONFIG_CRYPTO_TEST=m
 CONFIG_CRYPTO_HMAC=y
diff --git a/arch/parisc/configs/c3000_defconfig b/arch/parisc/configs/c3000_defconfig
index fb92b89..8e8f0e3 100644
--- a/arch/parisc/configs/c3000_defconfig
+++ b/arch/parisc/configs/c3000_defconfig
@@ -166,7 +166,6 @@ CONFIG_DEBUG_KERNEL=y
 CONFIG_DEBUG_MUTEXES=y
 # CONFIG_DEBUG_BUGVERBOSE is not set
 # CONFIG_RCU_CPU_STALL_DETECTOR is not set
-CONFIG_DEBUG_RODATA=y
 CONFIG_CRYPTO_NULL=m
 CONFIG_CRYPTO_TEST=m
 CONFIG_CRYPTO_MD5=m
diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index e02ada3..a055e5b 100644
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -545,7 +545,7 @@ void free_initmem(void)
 }
 
 
-#ifdef CONFIG_DEBUG_RODATA
+#ifdef CONFIG_STRICT_KERNEL_RWX
 void mark_rodata_ro(void)
 {
 	/* rodata memory was already mapped with KERNEL_RO access rights by
diff --git a/include/linux/filter.h b/include/linux/filter.h
index e4eb254..c2d2827 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -545,7 +545,7 @@ static inline bool bpf_prog_was_classic(const struct bpf_prog *prog)
 
 #define bpf_classic_proglen(fprog) (fprog->len * sizeof(fprog->filter[0]))
 
-#ifdef CONFIG_DEBUG_SET_MODULE_RONX
+#ifdef CONFIG_STRICT_MODULE_RWX
 static inline void bpf_prog_lock_ro(struct bpf_prog *fp)
 {
 	set_memory_ro((unsigned long)fp, fp->pages);
@@ -563,7 +563,7 @@ static inline void bpf_prog_lock_ro(struct bpf_prog *fp)
 static inline void bpf_prog_unlock_ro(struct bpf_prog *fp)
 {
 }
-#endif /* CONFIG_DEBUG_SET_MODULE_RONX */
+#endif /* CONFIG_STRICT_MODULE_RWX */
 
 int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap);
 static inline int sk_filter(struct sock *sk, struct sk_buff *skb)
diff --git a/include/linux/init.h b/include/linux/init.h
index 885c3e6..79af096 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -126,10 +126,10 @@ void prepare_namespace(void);
 void __init load_default_modules(void);
 int __init init_rootfs(void);
 
-#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX)
+#if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_STRICT_MODULE_RWX)
 extern bool rodata_enabled;
 #endif
-#ifdef CONFIG_DEBUG_RODATA
+#ifdef CONFIG_STRICT_KERNEL_RWX
 void mark_rodata_ro(void);
 #endif
 
diff --git a/include/linux/module.h b/include/linux/module.h
index 7c84273..d5afd14 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -764,7 +764,7 @@ extern int module_sysfs_initialized;
 
 #define __MODULE_STRING(x) __stringify(x)
 
-#ifdef CONFIG_DEBUG_SET_MODULE_RONX
+#ifdef CONFIG_STRICT_MODULE_RWX
 extern void set_all_modules_text_rw(void);
 extern void set_all_modules_text_ro(void);
 extern void module_enable_ro(const struct module *mod, bool after_init);
diff --git a/init/main.c b/init/main.c
index b0c9d6f..0b7bae2 100644
--- a/init/main.c
+++ b/init/main.c
@@ -925,7 +925,7 @@ static int try_to_run_init_process(const char *init_filename)
 
 static noinline void __init kernel_init_freeable(void);
 
-#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX)
+#if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_STRICT_MODULE_RWX)
 bool rodata_enabled __ro_after_init = true;
 static int __init set_debug_rodata(char *str)
 {
@@ -934,7 +934,7 @@ static int __init set_debug_rodata(char *str)
 __setup("rodata=", set_debug_rodata);
 #endif
 
-#ifdef CONFIG_DEBUG_RODATA
+#ifdef CONFIG_STRICT_KERNEL_RWX
 static void mark_readonly(void)
 {
 	if (rodata_enabled)
diff --git a/kernel/configs/android-recommended.config b/kernel/configs/android-recommended.config
index 297756b..99127ed 100644
--- a/kernel/configs/android-recommended.config
+++ b/kernel/configs/android-recommended.config
@@ -11,7 +11,7 @@ CONFIG_BLK_DEV_LOOP=y
 CONFIG_BLK_DEV_RAM=y
 CONFIG_BLK_DEV_RAM_SIZE=8192
 CONFIG_COMPACTION=y
-CONFIG_DEBUG_RODATA=y
+CONFIG_STRICT_KERNEL_RWX=y
 CONFIG_DM_CRYPT=y
 CONFIG_DM_UEVENT=y
 CONFIG_DM_VERITY=y
diff --git a/kernel/module.c b/kernel/module.c
index 38d4270..2643a14 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -74,9 +74,9 @@
 /*
  * Modules' sections will be aligned on page boundaries
  * to ensure complete separation of code and data, but
- * only when CONFIG_DEBUG_SET_MODULE_RONX=y
+ * only when CONFIG_STRICT_MODULE_RWX=y
  */
-#ifdef CONFIG_DEBUG_SET_MODULE_RONX
+#ifdef CONFIG_STRICT_MODULE_RWX
 # define debug_align(X) ALIGN(X, PAGE_SIZE)
 #else
 # define debug_align(X) (X)
@@ -1847,7 +1847,7 @@ static void mod_sysfs_teardown(struct module *mod)
 	mod_sysfs_fini(mod);
 }
 
-#ifdef CONFIG_DEBUG_SET_MODULE_RONX
+#ifdef CONFIG_STRICT_MODULE_RWX
 /*
  * LKM RO/NX protection: protect module's text/ro-data
  * from modification and any data from execution.
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index b26dbc4..86385af 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -1156,7 +1156,7 @@ static int __init hibernate_setup(char *str)
 	} else if (!strncmp(str, "no", 2)) {
 		noresume = 1;
 		nohibernate = 1;
-	} else if (IS_ENABLED(CONFIG_DEBUG_RODATA)
+	} else if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)
 		   && !strncmp(str, "protect_image", 13)) {
 		enable_restore_image_protection();
 	}
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 1dfa0da..7fdc40d 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -61,12 +61,12 @@ extern int hibernation_snapshot(int platform_mode);
 extern int hibernation_restore(int platform_mode);
 extern int hibernation_platform_enter(void);
 
-#ifdef CONFIG_DEBUG_RODATA
+#ifdef CONFIG_STRICT_KERNEL_RWX
 /* kernel/power/snapshot.c */
 extern void enable_restore_image_protection(void);
 #else
 static inline void enable_restore_image_protection(void) {}
-#endif /* CONFIG_DEBUG_RODATA */
+#endif /* CONFIG_STRICT_KERNEL_RWX */
 
 #else /* !CONFIG_HIBERNATION */
 
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 2d8e2b2..905d5bb 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -38,7 +38,7 @@
 
 #include "power.h"
 
-#ifdef CONFIG_DEBUG_RODATA
+#ifdef CONFIG_STRICT_KERNEL_RWX
 static bool hibernate_restore_protection;
 static bool hibernate_restore_protection_active;
 
@@ -73,7 +73,7 @@ static inline void hibernate_restore_protection_begin(void) {}
 static inline void hibernate_restore_protection_end(void) {}
 static inline void hibernate_restore_protect_page(void *page_address) {}
 static inline void hibernate_restore_unprotect_page(void *page_address) {}
-#endif /* CONFIG_DEBUG_RODATA */
+#endif /* CONFIG_STRICT_KERNEL_RWX */
 
 static int swsusp_page_is_free(struct page *);
 static void swsusp_set_page_forbidden(struct page *);
-- 
2.7.4

Re: [PATCHv2 1/2] arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common

[Mark Rutland]

On Fri, Feb 03, 2017 at 09:52:21AM -0800, Laura Abbott wrote:
> There are multiple architectures that support CONFIG_DEBUG_RODATA and
> CONFIG_SET_MODULE_RONX. These options also now have the ability to be
> turned off at runtime. Move these to an architecture independent
> location and make these options def_bool y for almost all of those
> arches.
> 
> Signed-off-by: Laura Abbott <labbott@redhat.com>

>From my POV this looks good. FWIW:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
> v2: This patch is now doing just the refactor of the existing config options.
> ---
>  arch/Kconfig              | 28 ++++++++++++++++++++++++++++
>  arch/arm/Kconfig          |  3 +++
>  arch/arm/Kconfig.debug    | 11 -----------
>  arch/arm/mm/Kconfig       | 12 ------------
>  arch/arm64/Kconfig        |  5 ++---
>  arch/arm64/Kconfig.debug  | 11 -----------
>  arch/parisc/Kconfig       |  1 +
>  arch/parisc/Kconfig.debug | 11 -----------
>  arch/s390/Kconfig         |  5 ++---
>  arch/s390/Kconfig.debug   |  3 ---
>  arch/x86/Kconfig          |  5 ++---
>  arch/x86/Kconfig.debug    | 11 -----------
>  12 files changed, 38 insertions(+), 68 deletions(-)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 99839c2..22ee01e 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -781,4 +781,32 @@ config VMAP_STACK
>  	  the stack to map directly to the KASAN shadow map using a formula
>  	  that is incorrect if the stack is in vmalloc space.
>  
> +config ARCH_NO_STRICT_RWX_DEFAULTS
> +	def_bool n
> +
> +config ARCH_HAS_STRICT_KERNEL_RWX
> +	def_bool n
> +
> +config DEBUG_RODATA
> +	def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
> +	prompt "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
> +	depends on ARCH_HAS_STRICT_KERNEL_RWX
> +	help
> +	  If this is set, kernel text and rodata memory will be made read-only,
> +	  and non-text memory will be made non-executable. This provides
> +	  protection against certain security exploits (e.g. executing the heap
> +	  or modifying text)
> +
> +config ARCH_HAS_STRICT_MODULE_RWX
> +	def_bool n
> +
> +config DEBUG_SET_MODULE_RONX
> +	def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
> +	prompt "Set loadable kenrel module data as NX and text as RO" if ARCH_NO_STRICT_RWX_DEFAULTS
> +	depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
> +	help
> +	  If this is set, module text and rodata memory will be made read-only,
> +	  and non-text memory will be made non-executable. This provides
> +	  protection against certain security exploits (e.g. writing to text)
> +
>  source "kernel/gcov/Kconfig"
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 186c4c2..aa73ca8 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -4,10 +4,13 @@ config ARM
>  	select ARCH_CLOCKSOURCE_DATA
>  	select ARCH_HAS_DEVMEM_IS_ALLOWED
>  	select ARCH_HAS_ELF_RANDOMIZE
> +	select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
> +	select ARCH_HAS_STRICT_MODULE_RWX if MMU
>  	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>  	select ARCH_HAVE_CUSTOM_GPIO_H
>  	select ARCH_HAS_GCOV_PROFILE_ALL
>  	select ARCH_MIGHT_HAVE_PC_PARPORT
> +	select ARCH_NO_STRICT_RWX_DEFAULTS if !CPU_V7
>  	select ARCH_SUPPORTS_ATOMIC_RMW
>  	select ARCH_USE_BUILTIN_BSWAP
>  	select ARCH_USE_CMPXCHG_LOCKREF
> diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
> index d83f7c3..426d271 100644
> --- a/arch/arm/Kconfig.debug
> +++ b/arch/arm/Kconfig.debug
> @@ -1738,17 +1738,6 @@ config PID_IN_CONTEXTIDR
>  	  additional instructions during context switch. Say Y here only if you
>  	  are planning to use hardware trace tools with this kernel.
>  
> -config DEBUG_SET_MODULE_RONX
> -	bool "Set loadable kernel module data as NX and text as RO"
> -	depends on MODULES && MMU
> -	---help---
> -	  This option helps catch unintended modifications to loadable
> -	  kernel module's text and read-only data. It also prevents execution
> -	  of module data. Such protection may interfere with run-time code
> -	  patching and dynamic kernel tracing - and they might also protect
> -	  against certain classes of kernel exploits.
> -	  If in doubt, say "N".
> -
>  source "drivers/hwtracing/coresight/Kconfig"
>  
>  endmenu
> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
> index f68e8ec..419a035 100644
> --- a/arch/arm/mm/Kconfig
> +++ b/arch/arm/mm/Kconfig
> @@ -1051,18 +1051,6 @@ config ARCH_SUPPORTS_BIG_ENDIAN
>  	  This option specifies the architecture can support big endian
>  	  operation.
>  
> -config DEBUG_RODATA
> -	bool "Make kernel text and rodata read-only"
> -	depends on MMU && !XIP_KERNEL
> -	default y if CPU_V7
> -	help
> -	  If this is set, kernel text and rodata memory will be made
> -	  read-only, and non-text kernel memory will be made non-executable.
> -	  The tradeoff is that each region is padded to section-size (1MiB)
> -	  boundaries (because their permissions are different and splitting
> -	  the 1M pages into 4K ones causes TLB performance problems), which
> -	  can waste memory.
> -
>  config DEBUG_ALIGN_RODATA
>  	bool "Make rodata strictly non-executable"
>  	depends on DEBUG_RODATA
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 1117421..e1efbcc 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -13,6 +13,8 @@ config ARM64
>  	select ARCH_HAS_GIGANTIC_PAGE
>  	select ARCH_HAS_KCOV
>  	select ARCH_HAS_SG_CHAIN
> +	select ARCH_HAS_STRICT_KERNEL_RWX
> +	select ARCH_HAS_STRICT_MODULE_RWX
>  	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>  	select ARCH_USE_CMPXCHG_LOCKREF
>  	select ARCH_SUPPORTS_ATOMIC_RMW
> @@ -123,9 +125,6 @@ config ARCH_PHYS_ADDR_T_64BIT
>  config MMU
>  	def_bool y
>  
> -config DEBUG_RODATA
> -	def_bool y
> -
>  config ARM64_PAGE_SHIFT
>  	int
>  	default 16 if ARM64_64K_PAGES
> diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> index d1ebd46..939815e 100644
> --- a/arch/arm64/Kconfig.debug
> +++ b/arch/arm64/Kconfig.debug
> @@ -71,17 +71,6 @@ config DEBUG_WX
>  
>  	  If in doubt, say "Y".
>  
> -config DEBUG_SET_MODULE_RONX
> -	bool "Set loadable kernel module data as NX and text as RO"
> -	depends on MODULES
> -	default y
> -	help
> -	  Is this is set, kernel module text and rodata will be made read-only.
> -	  This is to help catch accidental or malicious attempts to change the
> -	  kernel's executable code.
> -
> -	  If in doubt, say Y.
> -
>  config DEBUG_ALIGN_RODATA
>  	depends on DEBUG_RODATA
>  	bool "Align linker sections up to SECTION_SIZE"
> diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
> index 3a71f38..ad294b3 100644
> --- a/arch/parisc/Kconfig
> +++ b/arch/parisc/Kconfig
> @@ -8,6 +8,7 @@ config PARISC
>  	select HAVE_SYSCALL_TRACEPOINTS
>  	select ARCH_WANT_FRAME_POINTERS
>  	select ARCH_HAS_ELF_RANDOMIZE
> +	select ARCH_HAS_STRICT_KERNEL_RWX
>  	select RTC_CLASS
>  	select RTC_DRV_GENERIC
>  	select INIT_ALL_POSSIBLE
> diff --git a/arch/parisc/Kconfig.debug b/arch/parisc/Kconfig.debug
> index 68b7cbd..0d856b9 100644
> --- a/arch/parisc/Kconfig.debug
> +++ b/arch/parisc/Kconfig.debug
> @@ -5,15 +5,4 @@ source "lib/Kconfig.debug"
>  config TRACE_IRQFLAGS_SUPPORT
>  	def_bool y
>  
> -config DEBUG_RODATA
> -       bool "Write protect kernel read-only data structures"
> -       depends on DEBUG_KERNEL
> -       default y
> -       help
> -         Mark the kernel read-only data as write-protected in the pagetables,
> -         in order to catch accidental (and incorrect) writes to such const
> -         data. This option may have a slight performance impact because a
> -         portion of the kernel code won't be covered by a TLB anymore.
> -         If in doubt, say "N".
> -
>  endmenu
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index c6722112..53bb0e3 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -62,9 +62,6 @@ config PCI_QUIRKS
>  config ARCH_SUPPORTS_UPROBES
>  	def_bool y
>  
> -config DEBUG_RODATA
> -	def_bool y
> -
>  config S390
>  	def_bool y
>  	select ARCH_HAS_DEVMEM_IS_ALLOWED
> @@ -73,6 +70,8 @@ config S390
>  	select ARCH_HAS_GIGANTIC_PAGE
>  	select ARCH_HAS_KCOV
>  	select ARCH_HAS_SG_CHAIN
> +	select ARCH_HAS_STRICT_KERNEL_RWX
> +	select ARCH_HAS_STRICT_MODULE_RWX
>  	select ARCH_HAS_UBSAN_SANITIZE_ALL
>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG
>  	select ARCH_INLINE_READ_LOCK
> diff --git a/arch/s390/Kconfig.debug b/arch/s390/Kconfig.debug
> index 26c5d5be..57f8ea9 100644
> --- a/arch/s390/Kconfig.debug
> +++ b/arch/s390/Kconfig.debug
> @@ -17,7 +17,4 @@ config S390_PTDUMP
>  	  kernel.
>  	  If in doubt, say "N"
>  
> -config DEBUG_SET_MODULE_RONX
> -	def_bool y
> -	depends on MODULES
>  endmenu
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index e487493..13e1bf4 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -54,6 +54,8 @@ config X86
>  	select ARCH_HAS_MMIO_FLUSH
>  	select ARCH_HAS_PMEM_API		if X86_64
>  	select ARCH_HAS_SG_CHAIN
> +	select ARCH_HAS_STRICT_KERNEL_RWX
> +	select ARCH_HAS_STRICT_MODULE_RWX
>  	select ARCH_HAS_UBSAN_SANITIZE_ALL
>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG
>  	select ARCH_MIGHT_HAVE_ACPI_PDC		if ACPI
> @@ -309,9 +311,6 @@ config ARCH_SUPPORTS_UPROBES
>  config FIX_EARLYCON_MEM
>  	def_bool y
>  
> -config DEBUG_RODATA
> -	def_bool y
> -
>  config PGTABLE_LEVELS
>  	int
>  	default 4 if X86_64
> diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
> index 67eec55..69cdd0b 100644
> --- a/arch/x86/Kconfig.debug
> +++ b/arch/x86/Kconfig.debug
> @@ -109,17 +109,6 @@ config DEBUG_WX
>  
>  	  If in doubt, say "Y".
>  
> -config DEBUG_SET_MODULE_RONX
> -	bool "Set loadable kernel module data as NX and text as RO"
> -	depends on MODULES
> -	---help---
> -	  This option helps catch unintended modifications to loadable
> -	  kernel module's text and read-only data. It also prevents execution
> -	  of module data. Such protection may interfere with run-time code
> -	  patching and dynamic kernel tracing - and they might also protect
> -	  against certain classes of kernel exploits.
> -	  If in doubt, say "N".
> -
>  config DEBUG_NX_TEST
>  	tristate "Testcase for the NX non-executable stack feature"
>  	depends on DEBUG_KERNEL && m
> -- 
> 2.7.4
> 

Re: [PATCHv2 2/2] arch: Rename CONFIG_DEBUG_RODATA and CONFIG_DEBUG_MODULE_RONX

[Mark Rutland]

On Fri, Feb 03, 2017 at 09:52:22AM -0800, Laura Abbott wrote:
> 
> Both of these options are poorly named. The features they provide are
> necessary for system security and should not be considered debug only.
> Change the name to something that accurately describes what these
> options do.
> 
> Signed-off-by: Laura Abbott <labbott@redhat.com>

As with patch 1, this looks good to me. FWIW:

Acked-by: Mark Rutland <mark.rutland@arm.com>

> diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> index 939815e..560a8d8 100644
> --- a/arch/arm64/Kconfig.debug
> +++ b/arch/arm64/Kconfig.debug
> @@ -72,7 +72,7 @@ config DEBUG_WX
>  	  If in doubt, say "Y".
>  
>  config DEBUG_ALIGN_RODATA
> -	depends on DEBUG_RODATA
> +	depends on STRICT_KERNEL_RWX
>  	bool "Align linker sections up to SECTION_SIZE"
>  	help
>  	  If this option is enabled, sections that may potentially be marked as
> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
> index 94b62c1..67f9cb9 100644
> --- a/arch/arm64/kernel/insn.c
> +++ b/arch/arm64/kernel/insn.c
> @@ -93,7 +93,7 @@ static void __kprobes *patch_map(void *addr, int fixmap)
>  	bool module = !core_kernel_text(uintaddr);
>  	struct page *page;
>  
> -	if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
> +	if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
>  		page = vmalloc_to_page(addr);
>  	else if (!module)
>  		page = pfn_to_page(PHYS_PFN(__pa(addr)));

Since CONFIG_STRICT_MODULE_RWX is mandatory for arm64, we should be able
to simplify this, but that can wait for a later patch.

Thanks,
Mark.

Re: [PATCHv2 1/2] arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common

[Kees Cook]

On Fri, Feb 3, 2017 at 9:52 AM, Laura Abbott <labbott@redhat.com> wrote:
> There are multiple architectures that support CONFIG_DEBUG_RODATA and
> CONFIG_SET_MODULE_RONX. These options also now have the ability to be
> turned off at runtime. Move these to an architecture independent
> location and make these options def_bool y for almost all of those
> arches.
>
> Signed-off-by: Laura Abbott <labbott@redhat.com>
> ---
> v2: This patch is now doing just the refactor of the existing config options.
> ---
>  arch/Kconfig              | 28 ++++++++++++++++++++++++++++
>  arch/arm/Kconfig          |  3 +++
>  arch/arm/Kconfig.debug    | 11 -----------
>  arch/arm/mm/Kconfig       | 12 ------------
>  arch/arm64/Kconfig        |  5 ++---
>  arch/arm64/Kconfig.debug  | 11 -----------
>  arch/parisc/Kconfig       |  1 +
>  arch/parisc/Kconfig.debug | 11 -----------
>  arch/s390/Kconfig         |  5 ++---
>  arch/s390/Kconfig.debug   |  3 ---
>  arch/x86/Kconfig          |  5 ++---
>  arch/x86/Kconfig.debug    | 11 -----------
>  12 files changed, 38 insertions(+), 68 deletions(-)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 99839c2..22ee01e 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -781,4 +781,32 @@ config VMAP_STACK
>           the stack to map directly to the KASAN shadow map using a formula
>           that is incorrect if the stack is in vmalloc space.
>
> +config ARCH_NO_STRICT_RWX_DEFAULTS
> +       def_bool n
> +
> +config ARCH_HAS_STRICT_KERNEL_RWX
> +       def_bool n
> +
> +config DEBUG_RODATA
> +       def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
> +       prompt "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS

Ah! Yes, perfect. I totally forgot about using conditional "prompt" lines. Nice!

Acked-by: Kees Cook <keescook@chromium.org>

-Kees

-- 
Kees Cook
Pixel Security

Re: [PATCHv2 2/2] arch: Rename CONFIG_DEBUG_RODATA and CONFIG_DEBUG_MODULE_RONX

[Kees Cook]

On Fri, Feb 3, 2017 at 9:52 AM, Laura Abbott <labbott@redhat.com> wrote:
>
> Both of these options are poorly named. The features they provide are
> necessary for system security and should not be considered debug only.
> Change the name to something that accurately describes what these
> options do.

It may help to explicitly call out the name change from/to in the
commit message.

>
> Signed-off-by: Laura Abbott <labbott@redhat.com>
> ---
> [...]
> diff --git a/arch/arm/configs/aspeed_g4_defconfig b/arch/arm/configs/aspeed_g4_defconfig
> index ca39c04..beea2cc 100644
> --- a/arch/arm/configs/aspeed_g4_defconfig
> +++ b/arch/arm/configs/aspeed_g4_defconfig
> @@ -25,7 +25,6 @@ CONFIG_MODULE_UNLOAD=y
>  # CONFIG_ARCH_MULTI_V7 is not set
>  CONFIG_ARCH_ASPEED=y
>  CONFIG_MACH_ASPEED_G4=y
> -CONFIG_DEBUG_RODATA=y
>  CONFIG_AEABI=y
>  CONFIG_UACCESS_WITH_MEMCPY=y
>  CONFIG_SECCOMP=y

Are these defconfig cases correct (dropping DEBUG_RODATA without
adding STRICT_KERNEL_RWX)?

Who should carry this series, btw?

-Kees

-- 
Kees Cook
Pixel Security

Re: [PATCHv2 1/2] arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common

[Russell King - ARM Linux]

On Fri, Feb 03, 2017 at 11:45:56AM -0800, Kees Cook wrote:
> On Fri, Feb 3, 2017 at 9:52 AM, Laura Abbott <labbott@redhat.com> wrote:
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index 99839c2..22ee01e 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -781,4 +781,32 @@ config VMAP_STACK
> >           the stack to map directly to the KASAN shadow map using a formula
> >           that is incorrect if the stack is in vmalloc space.
> >
> > +config ARCH_NO_STRICT_RWX_DEFAULTS
> > +       def_bool n
> > +
> > +config ARCH_HAS_STRICT_KERNEL_RWX
> > +       def_bool n
> > +
> > +config DEBUG_RODATA
> > +       def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
> > +       prompt "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
> 
> Ah! Yes, perfect. I totally forgot about using conditional "prompt"
> lines. Nice!

It's no different from the more usual:

	bool "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
	default y if !ARCH_NO_STRICT_RWX_DEFAULTS
	depends on ARCH_HAS_STRICT_KERNEL_RWX

But... I really don't like this - way too many negations and negatives
which make it difficult to figure out what's going on here.

The situation we have today is:

-config DEBUG_RODATA
-       bool "Make kernel text and rodata read-only"
-       depends on MMU && !XIP_KERNEL
-       default y if CPU_V7

which is "allow the user to select DEBUG_RODATA if building a MMU non-XIP
kernel", suggesting that the user turns it on for ARMv7 CPUs.

That changes with this and the above:

+       select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
+       select ARCH_HAS_STRICT_MODULE_RWX if MMU
+       select ARCH_NO_STRICT_RWX_DEFAULTS if !CPU_V7

This means that ARCH_HAS_STRICT_KERNEL_RWX is set for a MMU non-XIP
kernel, which carries the same pre-condition for DEBUG_RODATA - no
problem there.

However, ARCH_NO_STRICT_RWX_DEFAULTS is set for non-ARMv7 CPUs, which
means the "Make kernel text and rodata read-only" prompt _is_ provided
for those.  However, for all ARMv7 systems, we go from "suggesting that
the user enables the option" to "you don't have a choice, you get this
whether you want it or not."

I'd prefer to keep it off for my development systems, where I don't
care about kernel security.  If we don't wish to do that as a general
rule, can we make it dependent on EMBEDDED?

Given that on ARM it can add up to 4MB to the kernel image - there
_will_ be about 1MB before the .text section, the padding on between
__modver and __ex_table which for me is around 626k, the padding
between .notes and the init sections start with .vectors (the space
between __ex_table and end of .notes is only 4124, which gets padded
up to 1MB) and lastly the padding between the .init section and the
data section (for me around 593k).  This all adds up to an increase
in kernel image size of 3.2MB on 14.2MB - an increase of 22%.

So no, I'm really not happy with that.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

Re: [PATCHv2 1/2] arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common

[Kees Cook]

On Fri, Feb 3, 2017 at 12:29 PM, Russell King - ARM Linux
<linux@armlinux.org.uk> wrote:
> On Fri, Feb 03, 2017 at 11:45:56AM -0800, Kees Cook wrote:
>> On Fri, Feb 3, 2017 at 9:52 AM, Laura Abbott <labbott@redhat.com> wrote:
>> > diff --git a/arch/Kconfig b/arch/Kconfig
>> > index 99839c2..22ee01e 100644
>> > --- a/arch/Kconfig
>> > +++ b/arch/Kconfig
>> > @@ -781,4 +781,32 @@ config VMAP_STACK
>> >           the stack to map directly to the KASAN shadow map using a formula
>> >           that is incorrect if the stack is in vmalloc space.
>> >
>> > +config ARCH_NO_STRICT_RWX_DEFAULTS
>> > +       def_bool n
>> > +
>> > +config ARCH_HAS_STRICT_KERNEL_RWX
>> > +       def_bool n
>> > +
>> > +config DEBUG_RODATA
>> > +       def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
>> > +       prompt "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
>>
>> Ah! Yes, perfect. I totally forgot about using conditional "prompt"
>> lines. Nice!
>
> It's no different from the more usual:
>
>         bool "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
>         default y if !ARCH_NO_STRICT_RWX_DEFAULTS
>         depends on ARCH_HAS_STRICT_KERNEL_RWX
>
> But... I really don't like this - way too many negations and negatives
> which make it difficult to figure out what's going on here.
>
> The situation we have today is:
>
> -config DEBUG_RODATA
> -       bool "Make kernel text and rodata read-only"
> -       depends on MMU && !XIP_KERNEL
> -       default y if CPU_V7
>
> which is "allow the user to select DEBUG_RODATA if building a MMU non-XIP
> kernel", suggesting that the user turns it on for ARMv7 CPUs.
>
> That changes with this and the above:
>
> +       select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
> +       select ARCH_HAS_STRICT_MODULE_RWX if MMU
> +       select ARCH_NO_STRICT_RWX_DEFAULTS if !CPU_V7
>
> This means that ARCH_HAS_STRICT_KERNEL_RWX is set for a MMU non-XIP
> kernel, which carries the same pre-condition for DEBUG_RODATA - no
> problem there.
>
> However, ARCH_NO_STRICT_RWX_DEFAULTS is set for non-ARMv7 CPUs, which
> means the "Make kernel text and rodata read-only" prompt _is_ provided
> for those.  However, for all ARMv7 systems, we go from "suggesting that
> the user enables the option" to "you don't have a choice, you get this
> whether you want it or not."
>
> I'd prefer to keep it off for my development systems, where I don't
> care about kernel security.  If we don't wish to do that as a general
> rule, can we make it dependent on EMBEDDED?
>
> Given that on ARM it can add up to 4MB to the kernel image - there
> _will_ be about 1MB before the .text section, the padding on between
> __modver and __ex_table which for me is around 626k, the padding
> between .notes and the init sections start with .vectors (the space
> between __ex_table and end of .notes is only 4124, which gets padded
> up to 1MB) and lastly the padding between the .init section and the
> data section (for me around 593k).  This all adds up to an increase
> in kernel image size of 3.2MB on 14.2MB - an increase of 22%.
>
> So no, I'm really not happy with that.

Ah yeah, good point. We have three cases: unsupported, mandatory,
optional, but we have the case of setting the default for the optional
case. Maybe something like this?

config STRICT_KERNEL_RWX
  bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
  depends on ARCH_HAS_STRICT_KERNEL_RWX
  default ARCH_OPTIONAL_KERNEL_RWX_DEFAULT

unsupported:
!ARCH_HAS_STRICT_KERNEL_RWX

mandatory:
ARCH_HAS_STRICT_KERNEL_RWX
!ARCH_OPTIONAL_KERNEL_RWX

optional:
ARCH_HAS_STRICT_KERNEL_RWX
ARCH_OPTIONAL_KERNEL_RWX
with default controlled by ARCH_OPTIONAL_KERNEL_RWX_DEFAULT

Then arm is:
  select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
  select ARCH_HAS_STRICT_MODULE_RWX if MMU
  select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
  select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7

x86 and arm64 are:
  select ARCH_HAS_STRICT_KERNEL_RWX
  select ARCH_HAS_STRICT_MODULE_RWX

?

-Kees

-- 
Kees Cook
Pixel Security

Re: [PATCHv2 1/2] arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common

[Russell King - ARM Linux]

On Fri, Feb 03, 2017 at 01:08:40PM -0800, Kees Cook wrote:
> On Fri, Feb 3, 2017 at 12:29 PM, Russell King - ARM Linux
> <linux@armlinux.org.uk> wrote:
> > On Fri, Feb 03, 2017 at 11:45:56AM -0800, Kees Cook wrote:
> >> On Fri, Feb 3, 2017 at 9:52 AM, Laura Abbott <labbott@redhat.com> wrote:
> >> > diff --git a/arch/Kconfig b/arch/Kconfig
> >> > index 99839c2..22ee01e 100644
> >> > --- a/arch/Kconfig
> >> > +++ b/arch/Kconfig
> >> > @@ -781,4 +781,32 @@ config VMAP_STACK
> >> >           the stack to map directly to the KASAN shadow map using a formula
> >> >           that is incorrect if the stack is in vmalloc space.
> >> >
> >> > +config ARCH_NO_STRICT_RWX_DEFAULTS
> >> > +       def_bool n
> >> > +
> >> > +config ARCH_HAS_STRICT_KERNEL_RWX
> >> > +       def_bool n
> >> > +
> >> > +config DEBUG_RODATA
> >> > +       def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
> >> > +       prompt "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
> >>
> >> Ah! Yes, perfect. I totally forgot about using conditional "prompt"
> >> lines. Nice!
> >
> > It's no different from the more usual:
> >
> >         bool "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
> >         default y if !ARCH_NO_STRICT_RWX_DEFAULTS
> >         depends on ARCH_HAS_STRICT_KERNEL_RWX
> >
> > But... I really don't like this - way too many negations and negatives
> > which make it difficult to figure out what's going on here.
> >
> > The situation we have today is:
> >
> > -config DEBUG_RODATA
> > -       bool "Make kernel text and rodata read-only"
> > -       depends on MMU && !XIP_KERNEL
> > -       default y if CPU_V7
> >
> > which is "allow the user to select DEBUG_RODATA if building a MMU non-XIP
> > kernel", suggesting that the user turns it on for ARMv7 CPUs.
> >
> > That changes with this and the above:
> >
> > +       select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
> > +       select ARCH_HAS_STRICT_MODULE_RWX if MMU
> > +       select ARCH_NO_STRICT_RWX_DEFAULTS if !CPU_V7
> >
> > This means that ARCH_HAS_STRICT_KERNEL_RWX is set for a MMU non-XIP
> > kernel, which carries the same pre-condition for DEBUG_RODATA - no
> > problem there.
> >
> > However, ARCH_NO_STRICT_RWX_DEFAULTS is set for non-ARMv7 CPUs, which
> > means the "Make kernel text and rodata read-only" prompt _is_ provided
> > for those.  However, for all ARMv7 systems, we go from "suggesting that
> > the user enables the option" to "you don't have a choice, you get this
> > whether you want it or not."
> >
> > I'd prefer to keep it off for my development systems, where I don't
> > care about kernel security.  If we don't wish to do that as a general
> > rule, can we make it dependent on EMBEDDED?
> >
> > Given that on ARM it can add up to 4MB to the kernel image - there
> > _will_ be about 1MB before the .text section, the padding on between
> > __modver and __ex_table which for me is around 626k, the padding
> > between .notes and the init sections start with .vectors (the space
> > between __ex_table and end of .notes is only 4124, which gets padded
> > up to 1MB) and lastly the padding between the .init section and the
> > data section (for me around 593k).  This all adds up to an increase
> > in kernel image size of 3.2MB on 14.2MB - an increase of 22%.
> >
> > So no, I'm really not happy with that.
> 
> Ah yeah, good point. We have three cases: unsupported, mandatory,
> optional, but we have the case of setting the default for the optional
> case. Maybe something like this?
> 
> config STRICT_KERNEL_RWX
>   bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
>   depends on ARCH_HAS_STRICT_KERNEL_RWX
>   default ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
> 
> unsupported:
> !ARCH_HAS_STRICT_KERNEL_RWX
> 
> mandatory:
> ARCH_HAS_STRICT_KERNEL_RWX
> !ARCH_OPTIONAL_KERNEL_RWX
> 
> optional:
> ARCH_HAS_STRICT_KERNEL_RWX
> ARCH_OPTIONAL_KERNEL_RWX
> with default controlled by ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
> 
> Then arm is:
>   select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
>   select ARCH_HAS_STRICT_MODULE_RWX if MMU
>   select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
>   select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
> 
> x86 and arm64 are:
>   select ARCH_HAS_STRICT_KERNEL_RWX
>   select ARCH_HAS_STRICT_MODULE_RWX

Looks to me like it will do the job.

In passing, I noticed that, on ARM:

  3 .rodata       002212b4  c0703000  c0703000  00703000  2**6
                  CONTENTS, ALLOC, LOAD, DATA

a lack of READONLY there - which suggests something in this lot isn't
actually read-only data:

        .rodata           : AT(ADDR(.rodata) - LOAD_OFFSET) {           \
                VMLINUX_SYMBOL(__start_rodata) = .;                     \
                *(.rodata) *(.rodata.*)                                 \
                RO_AFTER_INIT_DATA      /* Read only after init */      \
                KEEP(*(__vermagic))     /* Kernel version magic */      \
                . = ALIGN(8);                                           \
                VMLINUX_SYMBOL(__start___tracepoints_ptrs) = .;         \
                KEEP(*(__tracepoints_ptrs)) /* Tracepoints: pointer array */ \
                VMLINUX_SYMBOL(__stop___tracepoints_ptrs) = .;          \
                *(__tracepoints_strings)/* Tracepoints: strings */      \
        }                                                               \

I suspect it's the RO_AFTER_INIT_DATA section - maybe this should be
placed into its own separate output section?  I don't think it's doing
any harm, it's just odd that the .rodata section is marked as a normal
data section.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

Re: [PATCHv2 1/2] arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common

[Kees Cook]

On Fri, Feb 3, 2017 at 2:28 PM, Russell King - ARM Linux
<linux@armlinux.org.uk> wrote:
> On Fri, Feb 03, 2017 at 01:08:40PM -0800, Kees Cook wrote:
>> On Fri, Feb 3, 2017 at 12:29 PM, Russell King - ARM Linux
>> <linux@armlinux.org.uk> wrote:
>> > On Fri, Feb 03, 2017 at 11:45:56AM -0800, Kees Cook wrote:
>> >> On Fri, Feb 3, 2017 at 9:52 AM, Laura Abbott <labbott@redhat.com> wrote:
>> >> > diff --git a/arch/Kconfig b/arch/Kconfig
>> >> > index 99839c2..22ee01e 100644
>> >> > --- a/arch/Kconfig
>> >> > +++ b/arch/Kconfig
>> >> > @@ -781,4 +781,32 @@ config VMAP_STACK
>> >> >           the stack to map directly to the KASAN shadow map using a formula
>> >> >           that is incorrect if the stack is in vmalloc space.
>> >> >
>> >> > +config ARCH_NO_STRICT_RWX_DEFAULTS
>> >> > +       def_bool n
>> >> > +
>> >> > +config ARCH_HAS_STRICT_KERNEL_RWX
>> >> > +       def_bool n
>> >> > +
>> >> > +config DEBUG_RODATA
>> >> > +       def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
>> >> > +       prompt "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
>> >>
>> >> Ah! Yes, perfect. I totally forgot about using conditional "prompt"
>> >> lines. Nice!
>> >
>> > It's no different from the more usual:
>> >
>> >         bool "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
>> >         default y if !ARCH_NO_STRICT_RWX_DEFAULTS
>> >         depends on ARCH_HAS_STRICT_KERNEL_RWX
>> >
>> > But... I really don't like this - way too many negations and negatives
>> > which make it difficult to figure out what's going on here.
>> >
>> > The situation we have today is:
>> >
>> > -config DEBUG_RODATA
>> > -       bool "Make kernel text and rodata read-only"
>> > -       depends on MMU && !XIP_KERNEL
>> > -       default y if CPU_V7
>> >
>> > which is "allow the user to select DEBUG_RODATA if building a MMU non-XIP
>> > kernel", suggesting that the user turns it on for ARMv7 CPUs.
>> >
>> > That changes with this and the above:
>> >
>> > +       select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
>> > +       select ARCH_HAS_STRICT_MODULE_RWX if MMU
>> > +       select ARCH_NO_STRICT_RWX_DEFAULTS if !CPU_V7
>> >
>> > This means that ARCH_HAS_STRICT_KERNEL_RWX is set for a MMU non-XIP
>> > kernel, which carries the same pre-condition for DEBUG_RODATA - no
>> > problem there.
>> >
>> > However, ARCH_NO_STRICT_RWX_DEFAULTS is set for non-ARMv7 CPUs, which
>> > means the "Make kernel text and rodata read-only" prompt _is_ provided
>> > for those.  However, for all ARMv7 systems, we go from "suggesting that
>> > the user enables the option" to "you don't have a choice, you get this
>> > whether you want it or not."
>> >
>> > I'd prefer to keep it off for my development systems, where I don't
>> > care about kernel security.  If we don't wish to do that as a general
>> > rule, can we make it dependent on EMBEDDED?
>> >
>> > Given that on ARM it can add up to 4MB to the kernel image - there
>> > _will_ be about 1MB before the .text section, the padding on between
>> > __modver and __ex_table which for me is around 626k, the padding
>> > between .notes and the init sections start with .vectors (the space
>> > between __ex_table and end of .notes is only 4124, which gets padded
>> > up to 1MB) and lastly the padding between the .init section and the
>> > data section (for me around 593k).  This all adds up to an increase
>> > in kernel image size of 3.2MB on 14.2MB - an increase of 22%.
>> >
>> > So no, I'm really not happy with that.
>>
>> Ah yeah, good point. We have three cases: unsupported, mandatory,
>> optional, but we have the case of setting the default for the optional
>> case. Maybe something like this?
>>
>> config STRICT_KERNEL_RWX
>>   bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
>>   depends on ARCH_HAS_STRICT_KERNEL_RWX
>>   default ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
>>
>> unsupported:
>> !ARCH_HAS_STRICT_KERNEL_RWX
>>
>> mandatory:
>> ARCH_HAS_STRICT_KERNEL_RWX
>> !ARCH_OPTIONAL_KERNEL_RWX
>>
>> optional:
>> ARCH_HAS_STRICT_KERNEL_RWX
>> ARCH_OPTIONAL_KERNEL_RWX
>> with default controlled by ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
>>
>> Then arm is:
>>   select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
>>   select ARCH_HAS_STRICT_MODULE_RWX if MMU
>>   select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
>>   select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
>>
>> x86 and arm64 are:
>>   select ARCH_HAS_STRICT_KERNEL_RWX
>>   select ARCH_HAS_STRICT_MODULE_RWX
>
> Looks to me like it will do the job.
>
> In passing, I noticed that, on ARM:
>
>   3 .rodata       002212b4  c0703000  c0703000  00703000  2**6
>                   CONTENTS, ALLOC, LOAD, DATA
>
> a lack of READONLY there - which suggests something in this lot isn't
> actually read-only data:
>
>         .rodata           : AT(ADDR(.rodata) - LOAD_OFFSET) {           \
>                 VMLINUX_SYMBOL(__start_rodata) = .;                     \
>                 *(.rodata) *(.rodata.*)                                 \
>                 RO_AFTER_INIT_DATA      /* Read only after init */      \
>                 KEEP(*(__vermagic))     /* Kernel version magic */      \
>                 . = ALIGN(8);                                           \
>                 VMLINUX_SYMBOL(__start___tracepoints_ptrs) = .;         \
>                 KEEP(*(__tracepoints_ptrs)) /* Tracepoints: pointer array */ \
>                 VMLINUX_SYMBOL(__stop___tracepoints_ptrs) = .;          \
>                 *(__tracepoints_strings)/* Tracepoints: strings */      \
>         }                                                               \
>
> I suspect it's the RO_AFTER_INIT_DATA section - maybe this should be
> placed into its own separate output section?  I don't think it's doing
> any harm, it's just odd that the .rodata section is marked as a normal
> data section.

Yeah, I think the linker drops the RO flag when it see the
RO_AFTER_INIT_DATA flags. Since the kernel does the permissions
settings, this has been fine. If we can force the linker flags on it,
I'm all for it, but every time I've tried, it has defeated me. :)

-Kees

-- 
Kees Cook
Pixel Security

Re: [PATCHv2 1/2] arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common

[Laura Abbott]

On 02/03/2017 01:08 PM, Kees Cook wrote:
> On Fri, Feb 3, 2017 at 12:29 PM, Russell King - ARM Linux
> <linux@armlinux.org.uk> wrote:
>> On Fri, Feb 03, 2017 at 11:45:56AM -0800, Kees Cook wrote:
>>> On Fri, Feb 3, 2017 at 9:52 AM, Laura Abbott <labbott@redhat.com> wrote:
>>>> diff --git a/arch/Kconfig b/arch/Kconfig
>>>> index 99839c2..22ee01e 100644
>>>> --- a/arch/Kconfig
>>>> +++ b/arch/Kconfig
>>>> @@ -781,4 +781,32 @@ config VMAP_STACK
>>>>           the stack to map directly to the KASAN shadow map using a formula
>>>>           that is incorrect if the stack is in vmalloc space.
>>>>
>>>> +config ARCH_NO_STRICT_RWX_DEFAULTS
>>>> +       def_bool n
>>>> +
>>>> +config ARCH_HAS_STRICT_KERNEL_RWX
>>>> +       def_bool n
>>>> +
>>>> +config DEBUG_RODATA
>>>> +       def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
>>>> +       prompt "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
>>>
>>> Ah! Yes, perfect. I totally forgot about using conditional "prompt"
>>> lines. Nice!
>>
>> It's no different from the more usual:
>>
>>         bool "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
>>         default y if !ARCH_NO_STRICT_RWX_DEFAULTS
>>         depends on ARCH_HAS_STRICT_KERNEL_RWX
>>
>> But... I really don't like this - way too many negations and negatives
>> which make it difficult to figure out what's going on here.
>>
>> The situation we have today is:
>>
>> -config DEBUG_RODATA
>> -       bool "Make kernel text and rodata read-only"
>> -       depends on MMU && !XIP_KERNEL
>> -       default y if CPU_V7
>>
>> which is "allow the user to select DEBUG_RODATA if building a MMU non-XIP
>> kernel", suggesting that the user turns it on for ARMv7 CPUs.
>>
>> That changes with this and the above:
>>
>> +       select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
>> +       select ARCH_HAS_STRICT_MODULE_RWX if MMU
>> +       select ARCH_NO_STRICT_RWX_DEFAULTS if !CPU_V7
>>
>> This means that ARCH_HAS_STRICT_KERNEL_RWX is set for a MMU non-XIP
>> kernel, which carries the same pre-condition for DEBUG_RODATA - no
>> problem there.
>>
>> However, ARCH_NO_STRICT_RWX_DEFAULTS is set for non-ARMv7 CPUs, which
>> means the "Make kernel text and rodata read-only" prompt _is_ provided
>> for those.  However, for all ARMv7 systems, we go from "suggesting that
>> the user enables the option" to "you don't have a choice, you get this
>> whether you want it or not."
>>
>> I'd prefer to keep it off for my development systems, where I don't
>> care about kernel security.  If we don't wish to do that as a general
>> rule, can we make it dependent on EMBEDDED?
>>
>> Given that on ARM it can add up to 4MB to the kernel image - there
>> _will_ be about 1MB before the .text section, the padding on between
>> __modver and __ex_table which for me is around 626k, the padding
>> between .notes and the init sections start with .vectors (the space
>> between __ex_table and end of .notes is only 4124, which gets padded
>> up to 1MB) and lastly the padding between the .init section and the
>> data section (for me around 593k).  This all adds up to an increase
>> in kernel image size of 3.2MB on 14.2MB - an increase of 22%.
>>
>> So no, I'm really not happy with that.
> 
> Ah yeah, good point. We have three cases: unsupported, mandatory,
> optional, but we have the case of setting the default for the optional
> case. Maybe something like this?
> 
> config STRICT_KERNEL_RWX
>   bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
>   depends on ARCH_HAS_STRICT_KERNEL_RWX
>   default ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
> 
> unsupported:
> !ARCH_HAS_STRICT_KERNEL_RWX
> 
> mandatory:
> ARCH_HAS_STRICT_KERNEL_RWX
> !ARCH_OPTIONAL_KERNEL_RWX
> 
> optional:
> ARCH_HAS_STRICT_KERNEL_RWX
> ARCH_OPTIONAL_KERNEL_RWX
> with default controlled by ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
> 
> Then arm is:
>   select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
>   select ARCH_HAS_STRICT_MODULE_RWX if MMU
>   select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
>   select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
> 
> x86 and arm64 are:
>   select ARCH_HAS_STRICT_KERNEL_RWX
>   select ARCH_HAS_STRICT_MODULE_RWX
> 
> ?
> 
> -Kees
> 

Yes, that looks good. I wanted it to be mandatory to avoid the
mindset of "optional means we don't need it" but I see there
are some cases where it's better to turn it off. I'll see if
I can emphasize this properly in the help text ("Say Y here
unless you love security exploits running in production")

Thanks,
Laura

Re: [PATCHv2 2/2] arch: Rename CONFIG_DEBUG_RODATA and CONFIG_DEBUG_MODULE_RONX

[Laura Abbott]

On 02/03/2017 12:03 PM, Kees Cook wrote:
> On Fri, Feb 3, 2017 at 9:52 AM, Laura Abbott <labbott@redhat.com> wrote:
>>
>> Both of these options are poorly named. The features they provide are
>> necessary for system security and should not be considered debug only.
>> Change the name to something that accurately describes what these
>> options do.
> 
> It may help to explicitly call out the name change from/to in the
> commit message.
> 
>>
>> Signed-off-by: Laura Abbott <labbott@redhat.com>
>> ---
>> [...]
>> diff --git a/arch/arm/configs/aspeed_g4_defconfig b/arch/arm/configs/aspeed_g4_defconfig
>> index ca39c04..beea2cc 100644
>> --- a/arch/arm/configs/aspeed_g4_defconfig
>> +++ b/arch/arm/configs/aspeed_g4_defconfig
>> @@ -25,7 +25,6 @@ CONFIG_MODULE_UNLOAD=y
>>  # CONFIG_ARCH_MULTI_V7 is not set
>>  CONFIG_ARCH_ASPEED=y
>>  CONFIG_MACH_ASPEED_G4=y
>> -CONFIG_DEBUG_RODATA=y
>>  CONFIG_AEABI=y
>>  CONFIG_UACCESS_WITH_MEMCPY=y
>>  CONFIG_SECCOMP=y
> 
> Are these defconfig cases correct (dropping DEBUG_RODATA without
> adding STRICT_KERNEL_RWX)?
>

Yes, I think these need to be updated to the new config option since
these are not CPUv7


> Who should carry this series, btw?
> 

An excellent question :)

Would you be willing to carry it with Acks?

> -Kees
> 

Thanks,
Laura

Re: [PATCHv2 2/2] arch: Rename CONFIG_DEBUG_RODATA and CONFIG_DEBUG_MODULE_RONX

[Kees Cook]

On Mon, Feb 6, 2017 at 10:49 AM, Laura Abbott <labbott@redhat.com> wrote:
> On 02/03/2017 12:03 PM, Kees Cook wrote:
>> On Fri, Feb 3, 2017 at 9:52 AM, Laura Abbott <labbott@redhat.com> wrote:
>>>
>>> Both of these options are poorly named. The features they provide are
>>> necessary for system security and should not be considered debug only.
>>> Change the name to something that accurately describes what these
>>> options do.
>>
>> It may help to explicitly call out the name change from/to in the
>> commit message.
>>
>>>
>>> Signed-off-by: Laura Abbott <labbott@redhat.com>
>>> ---
>>> [...]
>>> diff --git a/arch/arm/configs/aspeed_g4_defconfig b/arch/arm/configs/aspeed_g4_defconfig
>>> index ca39c04..beea2cc 100644
>>> --- a/arch/arm/configs/aspeed_g4_defconfig
>>> +++ b/arch/arm/configs/aspeed_g4_defconfig
>>> @@ -25,7 +25,6 @@ CONFIG_MODULE_UNLOAD=y
>>>  # CONFIG_ARCH_MULTI_V7 is not set
>>>  CONFIG_ARCH_ASPEED=y
>>>  CONFIG_MACH_ASPEED_G4=y
>>> -CONFIG_DEBUG_RODATA=y
>>>  CONFIG_AEABI=y
>>>  CONFIG_UACCESS_WITH_MEMCPY=y
>>>  CONFIG_SECCOMP=y
>>
>> Are these defconfig cases correct (dropping DEBUG_RODATA without
>> adding STRICT_KERNEL_RWX)?
>>
>
> Yes, I think these need to be updated to the new config option since
> these are not CPUv7
>
>
>> Who should carry this series, btw?
>>
>
> An excellent question :)
>
> Would you be willing to carry it with Acks?

Yeah, I can push this via the KSPP tree: it's cross-architecture, so
it seems like this should go either through my tree or through akpm's
tree.

Are the arch maintainers okay with that?

-Kees

-- 
Kees Cook
Pixel Security

Re: [PATCHv2 1/2] arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common

[Pavel Machek]

[-- Attachment #1: Type: text/plain, Size: 5297 bytes --]

On Mon 2017-02-06 10:47:45, Laura Abbott wrote:
> On 02/03/2017 01:08 PM, Kees Cook wrote:
> > On Fri, Feb 3, 2017 at 12:29 PM, Russell King - ARM Linux
> > <linux@armlinux.org.uk> wrote:
> >> On Fri, Feb 03, 2017 at 11:45:56AM -0800, Kees Cook wrote:
> >>> On Fri, Feb 3, 2017 at 9:52 AM, Laura Abbott <labbott@redhat.com> wrote:
> >>>> diff --git a/arch/Kconfig b/arch/Kconfig
> >>>> index 99839c2..22ee01e 100644
> >>>> --- a/arch/Kconfig
> >>>> +++ b/arch/Kconfig
> >>>> @@ -781,4 +781,32 @@ config VMAP_STACK
> >>>>           the stack to map directly to the KASAN shadow map using a formula
> >>>>           that is incorrect if the stack is in vmalloc space.
> >>>>
> >>>> +config ARCH_NO_STRICT_RWX_DEFAULTS
> >>>> +       def_bool n
> >>>> +
> >>>> +config ARCH_HAS_STRICT_KERNEL_RWX
> >>>> +       def_bool n
> >>>> +
> >>>> +config DEBUG_RODATA
> >>>> +       def_bool y if !ARCH_NO_STRICT_RWX_DEFAULTS
> >>>> +       prompt "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
> >>>
> >>> Ah! Yes, perfect. I totally forgot about using conditional "prompt"
> >>> lines. Nice!
> >>
> >> It's no different from the more usual:
> >>
> >>         bool "Make kernel text and rodata read-only" if ARCH_NO_STRICT_RWX_DEFAULTS
> >>         default y if !ARCH_NO_STRICT_RWX_DEFAULTS
> >>         depends on ARCH_HAS_STRICT_KERNEL_RWX
> >>
> >> But... I really don't like this - way too many negations and negatives
> >> which make it difficult to figure out what's going on here.
> >>
> >> The situation we have today is:
> >>
> >> -config DEBUG_RODATA
> >> -       bool "Make kernel text and rodata read-only"
> >> -       depends on MMU && !XIP_KERNEL
> >> -       default y if CPU_V7
> >>
> >> which is "allow the user to select DEBUG_RODATA if building a MMU non-XIP
> >> kernel", suggesting that the user turns it on for ARMv7 CPUs.
> >>
> >> That changes with this and the above:
> >>
> >> +       select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
> >> +       select ARCH_HAS_STRICT_MODULE_RWX if MMU
> >> +       select ARCH_NO_STRICT_RWX_DEFAULTS if !CPU_V7
> >>
> >> This means that ARCH_HAS_STRICT_KERNEL_RWX is set for a MMU non-XIP
> >> kernel, which carries the same pre-condition for DEBUG_RODATA - no
> >> problem there.
> >>
> >> However, ARCH_NO_STRICT_RWX_DEFAULTS is set for non-ARMv7 CPUs, which
> >> means the "Make kernel text and rodata read-only" prompt _is_ provided
> >> for those.  However, for all ARMv7 systems, we go from "suggesting that
> >> the user enables the option" to "you don't have a choice, you get this
> >> whether you want it or not."
> >>
> >> I'd prefer to keep it off for my development systems, where I don't
> >> care about kernel security.  If we don't wish to do that as a general
> >> rule, can we make it dependent on EMBEDDED?
> >>
> >> Given that on ARM it can add up to 4MB to the kernel image - there
> >> _will_ be about 1MB before the .text section, the padding on between
> >> __modver and __ex_table which for me is around 626k, the padding
> >> between .notes and the init sections start with .vectors (the space
> >> between __ex_table and end of .notes is only 4124, which gets padded
> >> up to 1MB) and lastly the padding between the .init section and the
> >> data section (for me around 593k).  This all adds up to an increase
> >> in kernel image size of 3.2MB on 14.2MB - an increase of 22%.
> >>
> >> So no, I'm really not happy with that.
> > 
> > Ah yeah, good point. We have three cases: unsupported, mandatory,
> > optional, but we have the case of setting the default for the optional
> > case. Maybe something like this?
> > 
> > config STRICT_KERNEL_RWX
> >   bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
> >   depends on ARCH_HAS_STRICT_KERNEL_RWX
> >   default ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
> > 
> > unsupported:
> > !ARCH_HAS_STRICT_KERNEL_RWX
> > 
> > mandatory:
> > ARCH_HAS_STRICT_KERNEL_RWX
> > !ARCH_OPTIONAL_KERNEL_RWX
> > 
> > optional:
> > ARCH_HAS_STRICT_KERNEL_RWX
> > ARCH_OPTIONAL_KERNEL_RWX
> > with default controlled by ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
> > 
> > Then arm is:
> >   select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
> >   select ARCH_HAS_STRICT_MODULE_RWX if MMU
> >   select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
> >   select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
> > 
> > x86 and arm64 are:
> >   select ARCH_HAS_STRICT_KERNEL_RWX
> >   select ARCH_HAS_STRICT_MODULE_RWX
> > 
> > ?
> > 
> > -Kees
> > 
> 
> Yes, that looks good. I wanted it to be mandatory to avoid the
> mindset of "optional means we don't need it" but I see there
> are some cases where it's better to turn it off. I'll see if
> I can emphasize this properly in the help text ("Say Y here
> unless you love security exploits running in production")

What about fixing the memory wastage, instead? If you want something
almost-always-on, it should not waste megabytes of memory.

And BTW it is help text, not advertising for your favourite feature.
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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