Re: [PATCH 1/1] stackleak: Disable function tracing and kprobes for stackleak_erase()

[Masami Hiramatsu]

On Tue, 13 Nov 2018 00:08:48 +0300
Alexander Popov <alex.popov@xxxxxxxxx> wrote:

> The stackleak_erase() function is called on the trampoline stack at the end
> of syscall. This stack is not big enough for ftrace and kprobes operations,
> e.g. it can be exhausted if we use kprobe_events for stackleak_erase().
> 
> So let's disable function tracing and kprobes for stackleak_erase().
> 
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Signed-off-by: Alexander Popov <alex.popov@xxxxxxxxx>

Reviewed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

Thank you!

> ---
>  kernel/stackleak.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/stackleak.c b/kernel/stackleak.c
> index e428929..08cb57e 100644
> --- a/kernel/stackleak.c
> +++ b/kernel/stackleak.c
> @@ -11,6 +11,7 @@
>   */
>  
>  #include <linux/stackleak.h>
> +#include <linux/kprobes.h>
>  
>  #ifdef CONFIG_STACKLEAK_RUNTIME_DISABLE
>  #include <linux/jump_label.h>
> @@ -47,7 +48,7 @@ int stack_erasing_sysctl(struct ctl_table *table, int write,
>  #define skip_erasing()	false
>  #endif /* CONFIG_STACKLEAK_RUNTIME_DISABLE */
>  
> -asmlinkage void stackleak_erase(void)
> +asmlinkage void notrace stackleak_erase(void)
>  {
>  	/* It would be nice not to have 'kstack_ptr' and 'boundary' on stack */
>  	unsigned long kstack_ptr = current->lowest_stack;
> @@ -101,6 +102,7 @@ asmlinkage void stackleak_erase(void)
>  	/* Reset the 'lowest_stack' value for the next syscall */
>  	current->lowest_stack = current_top_of_stack() - THREAD_SIZE/64;
>  }
> +NOKPROBE_SYMBOL(stackleak_erase);
>  
>  void __used stackleak_track_stack(void)
>  {
> -- 
> 2.7.4
> 


-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>