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SubjectRe: [PATCH] kmemleak: clear stale pointers from task stacks
On Fri, Oct 06, 2017 at 02:38:21PM +0300, Konstantin Khlebnikov wrote:
> Kmemleak considers any pointers as task stacks as references.
^^
on

> This patch clears newly allocated and reused vmap stacks.
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> ---
> include/linux/thread_info.h | 2 +-
> kernel/fork.c | 4 ++++
> 2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
> index 905d769d8ddc..5f7eeab990fe 100644
> --- a/include/linux/thread_info.h
> +++ b/include/linux/thread_info.h
> @@ -42,7 +42,7 @@ enum {
> #define THREAD_ALIGN THREAD_SIZE
> #endif
>
> -#ifdef CONFIG_DEBUG_STACK_USAGE
> +#if IS_ENABLED(CONFIG_DEBUG_STACK_USAGE) || IS_ENABLED(CONFIG_DEBUG_KMEMLEAK)
> # define THREADINFO_GFP (GFP_KERNEL_ACCOUNT | __GFP_NOTRACK | \
> __GFP_ZERO)
> #else
> diff --git a/kernel/fork.c b/kernel/fork.c
> index c4ff0303b7c5..53e3b6f8a3bf 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -213,6 +213,10 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
> if (!s)
> continue;
>
> +#ifdef CONFIG_DEBUG_KMEMLEAK
> + /* Clear stale pointers from reused stack. */
> + memset(s->addr, 0, THREAD_SIZE);
> +#endif
> tsk->stack_vm_area = s;
> return s->addr;
> }

Acked-by: Catalin Marinas <catalin.marinas@arm.com>

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