From f504465970aebb2467da548f7c1efbbf36d0f44b Mon Sep 17 00:00:00 2001 From: Dmitry Antipov Date: Fri, 18 Oct 2024 08:13:38 +0300 Subject: [PATCH] net: sched: fix use-after-free in taprio_change() In 'taprio_change()', 'admin' pointer may become dangling due to sched switch / removal caused by 'advance_sched()', and critical section protected by 'q->current_entry_lock' is too small to prevent from such a scenario (which causes use-after-free detected by KASAN). Fix this by prefer 'rcu_replace_pointer()' over 'rcu_assign_pointer()' to update 'admin' immediately before an attempt to schedule freeing. Fixes: a3d43c0d56f1 ("taprio: Add support adding an admin schedule") Reported-by: syzbot+b65e0af58423fc8a73aa@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=b65e0af58423fc8a73aa Acked-by: Vinicius Costa Gomes Signed-off-by: Dmitry Antipov Link: https://patch.msgid.link/20241018051339.418890-1-dmantipov@yandex.ru Signed-off-by: Paolo Abeni --- net/sched/sch_taprio.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index 8498d0606b24..9f4e004cdb8b 100644 --- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c @@ -1965,7 +1965,8 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt, taprio_start_sched(sch, start, new_admin); - rcu_assign_pointer(q->admin_sched, new_admin); + admin = rcu_replace_pointer(q->admin_sched, new_admin, + lockdep_rtnl_is_held()); if (admin) call_rcu(&admin->rcu, taprio_free_sched_cb); -- 2.50.1