Re: [PATCH v4] rcu-tasks: Fix show_rcu_tasks_trace_gp_kthread buffer overflow

[Paul E. McKenney]

On Wed, Mar 27, 2024 at 01:52:46PM -0400, Steven Rostedt wrote:
> On Wed, 27 Mar 2024 20:47:47 +0300
> Nikita Kiryushin <kiryushin@xxxxxxxx> 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.
> > 
> > Use snprintf() with buffer size instead of sprintf().
> > 
> 
> Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>

Queued and pushed, thank you both!

							Thanx, Paul

> -- Steve
> 
> > 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>
> > ---
> > v4: Change ARRAY_SIZE to sizeof() as more idiomatic
> > as Steven Rostedt <rostedt@xxxxxxxxxxx> suggested
> > v3: Fixed commit message
> > v2: Use snprintf() as
> > Steven Rostedt <rostedt@xxxxxxxxxxx> suggested.
> >  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..2a453de9f3d9 100644
> > --- a/kernel/rcu/tasks.h
> > +++ b/kernel/rcu/tasks.h
> > @@ -1994,7 +1994,7 @@ void show_rcu_tasks_trace_gp_kthread(void)
> >  {
> >  	char buf[64];
> >  
> > -	sprintf(buf, "N%lu h:%lu/%lu/%lu",
> > +	snprintf(buf, sizeof(buf), "N%lu h:%lu/%lu/%lu",
> >  		data_race(n_trc_holdouts),
> >  		data_race(n_heavy_reader_ofl_updates),
> >  		data_race(n_heavy_reader_updates),
>