linux-kernel - Re: [PATCH] rcu-tasks: Update show_rcu_tasks_trace_gp

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Date: Tue, 26 Mar 2024 11:06:22 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Nikita Kiryushin <kiryushin@...ud.ru>
Cc: Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <quic_neeraju@...cinc.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>, rcu@...r.kernel.org,
	linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH] rcu-tasks: Update show_rcu_tasks_trace_gp_kthread buffer
 size

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@...ud.ru>

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
>