Merge tag 'hardening-v5.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull kernel hardening updates from Kees Cook:

 - Add arm64 Shadow Call Stack support for GCC 12 (Dan Li)

 - Avoid memset with stack offset randomization under Clang (Marco
   Elver)

 - Clean up stackleak plugin to play nice with .noinstr (Kees Cook)

 - Check stack depth for greater usercopy hardening coverage (Kees Cook)

* tag 'hardening-v5.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  arm64: Add gcc Shadow Call Stack support
  m68k: Implement "current_stack_pointer"
  xtensa: Implement "current_stack_pointer"
  usercopy: Check valid lifetime via stack depth
  stack: Constrain and fix stack offset randomization with Clang builds
  stack: Introduce CONFIG_RANDOMIZE_KSTACK_OFFSET
  gcc-plugins/stackleak: Ignore .noinstr.text and .entry.text
  gcc-plugins/stackleak: Exactly match strings instead of prefixes
  gcc-plugins/stackleak: Provide verbose mode

13 files changed, 48 insertions, 22 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 678a80713b21..cabfac22f2fb 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -599,21 +599,22 @@ config STACKPROTECTOR_STRONG
 config ARCH_SUPPORTS_SHADOW_CALL_STACK
 	bool
 	help
-	  An architecture should select this if it supports Clang's Shadow
-	  Call Stack and implements runtime support for shadow stack
+	  An architecture should select this if it supports the compiler's
+	  Shadow Call Stack and implements runtime support for shadow stack
 	  switching.
 
 config SHADOW_CALL_STACK
-	bool "Clang Shadow Call Stack"
-	depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
+	bool "Shadow Call Stack"
+	depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
 	depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
 	help
-	  This option enables Clang's Shadow Call Stack, which uses a
-	  shadow stack to protect function return addresses from being
-	  overwritten by an attacker. More information can be found in
-	  Clang's documentation:
+	  This option enables the compiler's Shadow Call Stack, which
+	  uses a shadow stack to protect function return addresses from
+	  being overwritten by an attacker. More information can be found
+	  in the compiler's documentation:
 
-	    https://clang.llvm.org/docs/ShadowCallStack.html
+	  - Clang: https://clang.llvm.org/docs/ShadowCallStack.html
+	  - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
 
 	  Note that security guarantees in the kernel differ from the
 	  ones documented for user space. The kernel must store addresses
@@ -1159,16 +1160,30 @@ config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
 	  to the compiler, so it will attempt to add canary checks regardless
 	  of the static branch state.
 
-config RANDOMIZE_KSTACK_OFFSET_DEFAULT
-	bool "Randomize kernel stack offset on syscall entry"
+config RANDOMIZE_KSTACK_OFFSET
+	bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
+	default y
 	depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
+	depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
 	help
 	  The kernel stack offset can be randomized (after pt_regs) by
 	  roughly 5 bits of entropy, frustrating memory corruption
 	  attacks that depend on stack address determinism or
-	  cross-syscall address exposures. This feature is controlled
-	  by kernel boot param "randomize_kstack_offset=on/off", and this
-	  config chooses the default boot state.
+	  cross-syscall address exposures.
+
+	  The feature is controlled via the "randomize_kstack_offset=on/off"
+	  kernel boot param, and if turned off has zero overhead due to its use
+	  of static branches (see JUMP_LABEL).
+
+	  If unsure, say Y.
+
+config RANDOMIZE_KSTACK_OFFSET_DEFAULT
+	bool "Default state of kernel stack offset randomization"
+	depends on RANDOMIZE_KSTACK_OFFSET
+	help
+	  Kernel stack offset randomization is controlled by kernel boot param
+	  "randomize_kstack_offset=on/off", and this config chooses the default
+	  boot state.
 
 config ARCH_OPTIONAL_KERNEL_RWX
 	def_bool n
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4c97cb40eebb..a7a09eef1852 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -5,6 +5,7 @@ config ARM
 	select ARCH_32BIT_OFF_T
 	select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE if HAVE_KRETPROBES && FRAME_POINTER && !ARM_UNWIND
 	select ARCH_HAS_BINFMT_FLAT
+	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DEBUG_VIRTUAL if MMU
 	select ARCH_HAS_DMA_WRITE_COMBINE if !ARM_DMA_MEM_BUFFERABLE
 	select ARCH_HAS_ELF_RANDOMIZE
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index a555f409ba95..8c54de0cf3d6 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -19,6 +19,7 @@ config ARM64
 	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2
 	select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
 	select ARCH_HAS_CACHE_LINE_SIZE
+	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DEBUG_VIRTUAL
 	select ARCH_HAS_DEBUG_VM_PGTABLE
 	select ARCH_HAS_DMA_PREP_COHERENT
@@ -1257,7 +1258,7 @@ config HW_PERF_EVENTS
 	def_bool y
 	depends on ARM_PMU
 
-# Supported by clang >= 7.0
+# Supported by clang >= 7.0 or GCC >= 12.0.0
 config CC_HAVE_SHADOW_CALL_STACK
 	def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)
 
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index 268b3860d40d..936cce42ae9a 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -4,6 +4,7 @@ config M68K
 	default y
 	select ARCH_32BIT_OFF_T
 	select ARCH_HAS_BINFMT_FLAT
+	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DMA_PREP_COHERENT if HAS_DMA && MMU && !COLDFIRE
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if HAS_DMA
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG if RMW_INSNS
diff --git a/arch/m68k/include/asm/current.h b/arch/m68k/include/asm/current.h
index 6390ef2f7f86..c117907e1276 100644
--- a/arch/m68k/include/asm/current.h
+++ b/arch/m68k/include/asm/current.h
@@ -24,6 +24,8 @@ static inline struct task_struct *get_current(void)
 
 #define	current	get_current()
 
-#endif /* CONFNIG_MMU */
+#endif /* CONFIG_MMU */
+
+register unsigned long current_stack_pointer __asm__("sp");
 
 #endif /* !(_M68K_CURRENT_H) */
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index b779603978e1..7e7387bd7d53 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -108,6 +108,7 @@ config PPC
 	select ARCH_ENABLE_MEMORY_HOTPLUG
 	select ARCH_ENABLE_MEMORY_HOTREMOVE
 	select ARCH_HAS_COPY_MC			if PPC64
+	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DEBUG_VIRTUAL
 	select ARCH_HAS_DEBUG_VM_PGTABLE
 	select ARCH_HAS_DEBUG_WX		if STRICT_KERNEL_RWX
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index be9f39fd06df..4845ab549dd1 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -60,6 +60,7 @@ config S390
 	select ARCH_ENABLE_MEMORY_HOTPLUG if SPARSEMEM
 	select ARCH_ENABLE_MEMORY_HOTREMOVE
 	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2
+	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DEBUG_VM_PGTABLE
 	select ARCH_HAS_DEBUG_WX
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 2474a04ceac4..1c2b53bf3093 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -7,6 +7,7 @@ config SUPERH
 	select ARCH_HAVE_CUSTOM_GPIO_H
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG if (GUSA_RB || CPU_SH4A)
 	select ARCH_HAS_BINFMT_FLAT if !MMU
+	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_GIGANTIC_PAGE
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_PTE_SPECIAL
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 015da1de1234..327e045540fa 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -69,6 +69,7 @@ config X86
 	select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
 	select ARCH_HAS_ACPI_TABLE_UPGRADE	if ACPI
 	select ARCH_HAS_CACHE_LINE_SIZE
+	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DEBUG_VIRTUAL
 	select ARCH_HAS_DEBUG_VM_PGTABLE	if !X86_PAE
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index 8ac599aa6d99..887432327613 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -3,6 +3,7 @@ config XTENSA
 	def_bool y
 	select ARCH_32BIT_OFF_T
 	select ARCH_HAS_BINFMT_FLAT if !MMU
+	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DMA_PREP_COHERENT if MMU
 	select ARCH_HAS_SYNC_DMA_FOR_CPU if MMU
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if MMU
diff --git a/arch/xtensa/include/asm/current.h b/arch/xtensa/include/asm/current.h
index 5d98a7ad4251..08010dbf5e09 100644
--- a/arch/xtensa/include/asm/current.h
+++ b/arch/xtensa/include/asm/current.h
@@ -26,6 +26,8 @@ static inline struct task_struct *get_current(void)
 
 #define current get_current()
 
+register unsigned long current_stack_pointer __asm__("a1");
+
 #else
 
 #define GET_CURRENT(reg,sp)		\
diff --git a/arch/xtensa/include/asm/stacktrace.h b/arch/xtensa/include/asm/stacktrace.h
index fe06e8ed162b..a85e785a6288 100644
--- a/arch/xtensa/include/asm/stacktrace.h
+++ b/arch/xtensa/include/asm/stacktrace.h
@@ -19,14 +19,14 @@ struct stackframe {
 
 static __always_inline unsigned long *stack_pointer(struct task_struct *task)
 {
-	unsigned long *sp;
+	unsigned long sp;
 
 	if (!task || task == current)
-		__asm__ __volatile__ ("mov %0, a1\n" : "=a"(sp));
+		sp = current_stack_pointer;
 	else
-		sp = (unsigned long *)task->thread.sp;
+		sp = task->thread.sp;
 
-	return sp;
+	return (unsigned long *)sp;
 }
 
 void walk_stackframe(unsigned long *sp,
diff --git a/arch/xtensa/kernel/irq.c b/arch/xtensa/kernel/irq.c
index 15051a8a1539..529fe9245821 100644
--- a/arch/xtensa/kernel/irq.c
+++ b/arch/xtensa/kernel/irq.c
@@ -36,9 +36,8 @@ asmlinkage void do_IRQ(int hwirq, struct pt_regs *regs)
 #ifdef CONFIG_DEBUG_STACKOVERFLOW
 	/* Debugging check for stack overflow: is there less than 1KB free? */
 	{
-		unsigned long sp;
+		unsigned long sp = current_stack_pointer;
 
-		__asm__ __volatile__ ("mov %0, a1\n" : "=a" (sp));
 		sp &= THREAD_SIZE - 1;
 
 		if (unlikely(sp < (sizeof(thread_info) + 1024)))