[PATCH RFC 4/8] kasan: unpoison stack only with CONFIG_KASAN_STACK

From: Andrey Konovalov
Date: Wed Oct 14 2020 - 16:45:13 EST


There's a config option CONFIG_KASAN_STACK that has to be enabled for
KASAN to use stack instrumentation and perform validity checks for
stack variables.

There's no need to unpoison stack when CONFIG_KASAN_STACK is not enabled.
Only call kasan_unpoison_task_stack[_below]() when CONFIG_KASAN_STACK is
enabled.

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Link: https://linux-review.googlesource.com/id/If8a891e9fe01ea543e00b576852685afec0887e3
---
arch/arm64/kernel/sleep.S | 2 +-
arch/x86/kernel/acpi/wakeup_64.S | 2 +-
include/linux/kasan.h | 10 ++++++----
mm/kasan/common.c | 2 ++
4 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index ba40d57757d6..bdadfa56b40e 100644
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S
@@ -133,7 +133,7 @@ SYM_FUNC_START(_cpu_resume)
*/
bl cpu_do_resume

-#ifdef CONFIG_KASAN
+#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
mov x0, sp
bl kasan_unpoison_task_stack_below
#endif
diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
index c8daa92f38dc..5d3a0b8fd379 100644
--- a/arch/x86/kernel/acpi/wakeup_64.S
+++ b/arch/x86/kernel/acpi/wakeup_64.S
@@ -112,7 +112,7 @@ SYM_FUNC_START(do_suspend_lowlevel)
movq pt_regs_r14(%rax), %r14
movq pt_regs_r15(%rax), %r15

-#ifdef CONFIG_KASAN
+#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
/*
* The suspend path may have poisoned some areas deeper in the stack,
* which we now need to unpoison.
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 3f3f541e5d5f..7be9fb9146ac 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -68,8 +68,6 @@ static inline void kasan_disable_current(void) {}

void kasan_unpoison_memory(const void *address, size_t size);

-void kasan_unpoison_task_stack(struct task_struct *task);
-
void kasan_alloc_pages(struct page *page, unsigned int order);
void kasan_free_pages(struct page *page, unsigned int order);

@@ -114,8 +112,6 @@ void kasan_restore_multi_shot(bool enabled);

static inline void kasan_unpoison_memory(const void *address, size_t size) {}

-static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
-
static inline void kasan_alloc_pages(struct page *page, unsigned int order) {}
static inline void kasan_free_pages(struct page *page, unsigned int order) {}

@@ -167,6 +163,12 @@ static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }

#endif /* CONFIG_KASAN */

+#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
+void kasan_unpoison_task_stack(struct task_struct *task);
+#else
+static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
+#endif
+
#ifdef CONFIG_KASAN_GENERIC

void kasan_cache_shrink(struct kmem_cache *cache);
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index a880e5a547ed..a3e67d49b893 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -58,6 +58,7 @@ void kasan_disable_current(void)
}
#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */

+#if CONFIG_KASAN_STACK
static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
{
void *base = task_stack_page(task);
@@ -84,6 +85,7 @@ asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)

kasan_unpoison_memory(base, watermark - base);
}
+#endif /* CONFIG_KASAN_STACK */

void kasan_alloc_pages(struct page *page, unsigned int order)
{
--
2.28.0.1011.ga647a8990f-goog