netdev - Re: [PATCH] net/sched: fix use-after-free in taprio_dev

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Message-ID: <CANn89iJiLKn8Nb8mnTHowBM3UumJQrwKHPam0JYGfo482DoE-w@mail.gmail.com>
Date: Wed, 11 Jun 2025 04:01:50 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Hyunwoo Kim <imv4bel@...il.com>, Vladimir Oltean <vladimir.oltean@....com>
Cc: vinicius.gomes@...el.com, jhs@...atatu.com, xiyou.wangcong@...il.com, 
	jiri@...nulli.us, davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, 
	horms@...nel.org, netdev@...r.kernel.org, v4bel@...ori.io
Subject: Re: [PATCH] net/sched: fix use-after-free in taprio_dev_notifier

On Wed, Jun 11, 2025 at 3:03 AM Hyunwoo Kim <imv4bel@...il.com> wrote:
>
> Since taprio’s taprio_dev_notifier() isn’t protected by an
> RCU read-side critical section, a race with advance_sched()
> can lead to a use-after-free.
>
> Adding rcu_read_lock() inside taprio_dev_notifier() prevents this.
>
> Signed-off-by: Hyunwoo Kim <imv4bel@...il.com>

Looks good to me, but we need a Fixes: tag and/or a CC: stable@ o make
sure this patch reaches appropriate stable trees.

Also please CC the author of the  patch.

It seems bug came with

commit fed87cc6718ad5f80aa739fee3c5979a8b09d3a6
Author: Vladimir Oltean <vladimir.oltean@....com>
Date:   Tue Feb 7 15:54:38 2023 +0200

    net/sched: taprio: automatically calculate queueMaxSDU based on TC
gate durations




> ---
>  net/sched/sch_taprio.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
> index 14021b812329..bd2b02d1dc63 100644
> --- a/net/sched/sch_taprio.c
> +++ b/net/sched/sch_taprio.c
> @@ -1320,6 +1320,7 @@ static int taprio_dev_notifier(struct notifier_block *nb, unsigned long event,
>         if (event != NETDEV_UP && event != NETDEV_CHANGE)
>                 return NOTIFY_DONE;
>
> +       rcu_read_lock();
>         list_for_each_entry(q, &taprio_list, taprio_list) {
>                 if (dev != qdisc_dev(q->root))
>                         continue;
> @@ -1328,16 +1329,17 @@ static int taprio_dev_notifier(struct notifier_block *nb, unsigned long event,
>
>                 stab = rtnl_dereference(q->root->stab);
>
> -               oper = rtnl_dereference(q->oper_sched);
> +               oper = rcu_dereference(q->oper_sched);
>                 if (oper)
>                         taprio_update_queue_max_sdu(q, oper, stab);
>
> -               admin = rtnl_dereference(q->admin_sched);
> +               admin = rcu_dereference(q->admin_sched);
>                 if (admin)
>                         taprio_update_queue_max_sdu(q, admin, stab);
>
>                 break;
>         }
> +       rcu_read_unlock();
>
>         return NOTIFY_DONE;
>  }
> --
> 2.34.1
>