2024-03-27 18:23:29

by Steven Rostedt

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

On Wed, 27 Mar 2024 20:47:47 +0300
Nikita Kiryushin <[email protected]> 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) <[email protected]>

-- 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 <[email protected]>
> ---
> v4: Change ARRAY_SIZE to sizeof() as more idiomatic
> as Steven Rostedt <[email protected]> suggested
> v3: Fixed commit message
> v2: Use snprintf() as
> Steven Rostedt <[email protected]> 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),

2024-03-27 18:31:09

by Paul E. McKenney

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

On Wed, Mar 27, 2024 at 01:52:46PM -0400, Steven Rostedt wrote:
> On Wed, 27 Mar 2024 20:47:47 +0300
> Nikita Kiryushin <[email protected]> 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) <[email protected]>

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 <[email protected]>
> > ---
> > v4: Change ARRAY_SIZE to sizeof() as more idiomatic
> > as Steven Rostedt <[email protected]> suggested
> > v3: Fixed commit message
> > v2: Use snprintf() as
> > Steven Rostedt <[email protected]> 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),
>