Re: [PATCH] rcu-tasks: Update show_rcu_tasks_trace_gp_kthread buffer size

[Paul E. McKenney]

On Tue, Mar 26, 2024 at 08:48:39PM +0300, Nikita Kiryushin wrote:
> There is a possibility of buffer overflow in
> show_rcu_tasks_trace_gp_kthread() if counters, passed
> to sprintf() are huge. Counter numbers, needed for this
> are unrealistically high, but buffer overflow is still
> possible.
> 
> Update used buffer size for maximum needed size for
> current format string.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: edf3775f0ad6 ("rcu-tasks: Add count for idle tasks on offline CPUs")
> Signed-off-by: Nikita Kiryushin <kiryushin@xxxxxxxx>

Good catch!  Applied for testing and further review.

							Thanx, Paul

> ---
>  kernel/rcu/tasks.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> index 147b5945d67a..13ac514489c0 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -1992,7 +1992,7 @@ static int __init rcu_spawn_tasks_trace_kthread(void)
>  #if !defined(CONFIG_TINY_RCU)
>  void show_rcu_tasks_trace_gp_kthread(void)
>  {
> -	char buf[64];
> +	char buf[87];
>  
>  	sprintf(buf, "N%lu h:%lu/%lu/%lu",
>  		data_race(n_trc_holdouts),
> -- 
> 2.34.1
>