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    Subject[PATCH RFC v2 04/21] kasan: unpoison stack only with CONFIG_KASAN_STACK
    From
    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@google.com>
    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)
    {
    --
    2.29.0.rc1.297.gfa9743e501-goog
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